485BPOS

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT

UNDER

SECURITIES ACT OF 1933	☒
Pre-Effective Amendment No.	☐
Post-Effective Amendment No. 86	☒

REGISTRATION STATEMENT

UNDER

THE INVESTMENT COMPANY ACT OF 1940	☒
Amendment No. 66	☒

PENN SERIES FUNDS, INC.

(Exact Name of Registrant as Specified in Charter)

600 Dresher Road

Horsham, Pennsylvania 19044

(Address of Principal Executive Offices)

Registrant’s Telephone Number: 215-956-8000

Copies to:

DAVID M. O’MALLEY President Penn Series Funds, Inc. 600 Dresher Road Horsham, Pennsylvania 19044	CHRISTOPHER D. MENCONI LAURA E. FLORES Morgan, Lewis & Bockius LLP 1111 Pennsylvania Avenue NW Washington, DC 20004
(Name and Address of Agent for Service)

It is proposed that this filing will become effective (check appropriate box):

☒ Immediately upon filing pursuant to paragraph (b) of Rule 485

☐ On [date] pursuant to paragraph (b) of Rule 485

☐ 60 days after filing pursuant to paragraph (a)(1) of Rule 485

☐ On [date] pursuant to paragraph (a)(1) of Rule 485

☐ 75 days after filing pursuant to paragraph (a)(2) of Rule 485

☐ On [date] pursuant to paragraph (a)(2) of Rule 485

EXPLANATORY NOTE

This Post-Effective Amendment No. 86 relates to each series of Penn Series Funds, Inc. (the “Company”). The sole purpose of this filing is to file as an exhibit to the Company’s registration statement, risk/return information in interactive data format for each series of the Company.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended (the “1933 Act”), and the Investment Company Act of 1940, as amended, the Registrant certifies that it meets all of the requirements for effectiveness of this Registration Statement pursuant to Rule 485(b) under the 1933 Act and that it has duly caused this Post-Effective Amendment No. 86 to the Registration Statement on Form N-1A to be signed on its behalf by the undersigned, thereunto duly authorized, in the Township of Horsham and Commonwealth of Pennsylvania, on this 15^th day of May, 2018.

PENN SERIES FUNDS, INC.
	(Registrant)
By:	/s/ David M. O’Malley
	David M. O’Malley, President

Pursuant to the requirements of the 1933 Act, this Post-Effective Amendment No. 86 to the Registration Statement on Form N-1A has been signed below by the following persons in the capacities indicated on the 15^th day of May, 2018.

Signature	Title
/s/ David M. O’Malley	President (Principal Executive Officer)
David M. O’Malley
/s/ Steven Viola	Treasurer (Principal Financial Officer and Principal Accounting Officer)
Steven Viola
/s/ Eileen C. McDonnell	Director
Eileen C. McDonnell
* Joanne B. Mack	Director
* David B. Pudlin	Director
* Archie Craig MacKinlay	Director
* Rebecca Matthias	Director
* Marie K. Karpinski	Director

*By:	/s/ Eileen C. McDonnell
	Eileen C. McDonnell, Attorney-In-Fact

SCHEDULE OF EXHIBITS TO FORM N-1A

Penn Series Funds, Inc.

Exhibit Number	Exhibit
EX-101.INS	XBRL Instance Document
EX-101.SCH	XBRL Taxonomy Extension Schema Document
EX-101.CAL	XBRL Taxonomy Extension Calculation Linkbase
EX-101.DEF	XBRL Taxonomy Extension Definition Linkbase
EX-101.LAB	XBRL Taxonomy Extension Labels Linkbase
EX-101.PRE	XBRL Taxonomy Extension Presentation Linkbase

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	Dec. 31, 2017
Registrant Name	dei_EntityRegistrantName	PENN SERIES FUNDS INC
Central Index Key	dei_EntityCentralIndexKey	0000702340
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Apr. 26, 2018
Document Effective Date	dei_DocumentEffectiveDate	May 01, 2018
Prospectus Date	rr_ProspectusDate	May 01, 2018

XML

Penn Series Money Market Fund

FUND SUMMARY:  MONEY MARKET FUND

Investment Objective

The Money Market Fund (the “Fund”) seeks current income, while preserving capital and liquidity.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable annuity contract or variable life insurance policy (each, a “variable contract”) level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Money Market Fund Money Market Fund
Investment Advisory Fees	0.33%
Distribution (12b-1) Fees	none
Other Expenses	0.26%
Acquired Fund Fees and Expenses	0.01%
Total Annual Fund Operating Expenses	0.60%	[1]

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Money Market Fund | Money Market Fund | USD ($)	61	192	335	750

Principal Investment Strategy

The Fund will invest no less than 99.5% of its total assets in government securities, cash or repurchase agreements that are collateralized fully by government securities or cash.

Government securities generally are securities that are issued or guaranteed as to principal and interest by the U.S. Government or by one of its agencies or instrumentalities. Some government securities are backed by the full faith and credit of the U.S. Government. Some government securities are not backed by the full faith and credit of the U.S. Government but rather are supported by the issuer’s ability to borrow from the U.S. Treasury, by only the credit of the issuer, or by the United States in some other way. The Fund intends to operate as a “government money market fund” in compliance with Rule 2a-7 under the Investment Company Act of 1940, as amended (the “1940 Act”).

Under Rule 2a-7, the Fund may invest only in U.S. dollar-denominated securities that are determined to present minimal credit risk and meet certain other criteria, including relating to maturity, diversification, liquidity and credit quality. For example, the Fund invests in securities that generally have remaining maturities of 397 days or less and will have a dollar-weighted average portfolio maturity of 60 days or less and a dollar-weighted average life to maturity of 120 days or less. The Fund also maintains sufficient portfolio liquidity to meet reasonably foreseeable redemption requests. The Fund seeks to maintain a stable net asset value (“NAV”) of $1.00 per share and its portfolio is valued using the amortized cost method as permitted by Rule 2a-7. As a government money market fund, the Fund is not required to impose liquidity fees or redemptions gates. The Fund’s Board, however, may elect to impose such fees or gates in the future if it believes such measures are appropriate and in the best interests of the Fund and its shareholders.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Counterparty Risk.  The possibility that a party to a transaction involving the Fund may fail to meet its obligations thereby causing the Fund to lose money or the benefit of the transaction or preventing the Fund from selling or buying other securities to implement its investment strategies.

Credit Risk.  The possibility that an issuer of a debt security held by the Fund defaults on its payment obligations. While the Fund tries to minimize this risk by investing in high-quality securities, the credit quality of such securities may change rapidly in certain market environments and in response to certain market events, such as a decline in the credit quality of an issuer.

Income Risk.  The possibility that the Fund’s yield (the rate of dividends the Fund pays) may decline in the event of declining interest rates.

Interest Rate Risk.  The possibility that the prices of the Fund’s fixed income investments will decline due to rising interest rates.

Investment Risk.  You could lose money by investing in the Fund. Although the Fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so. An investment in the Fund is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency. Penn Mutual Asset Management, LLC (“PMAM” or the “Adviser”), the Fund’s sponsor, and its affiliates have no legal obligation to provide financial support to the Fund, and you should not expect that PMAM or its affiliates will provide financial support to the Fund at any time.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Redemption Risk.  The possibility that large redemptions may cause the Fund to sell its securities at inopportune times resulting in a loss to the Fund.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by the Fund if it is not obligated to do so because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause the Fund’s share price or yield to fall.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Prior to May 1, 2016, the Fund invested in a diversified portfolio of high-quality money market instruments of a variety of issuers. Effective May 1, 2016, the Fund operates as a “government money market fund” and as such is limited to investing 99.5% of its total assets in government securities, cash or repurchase agreements that are collateralized fully by government securities or cash. Accordingly, the performance information below may have been different if the current investment strategy had been in effect during the period prior to the Fund’s conversion to a government money market fund. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower. The current yield of the Money Market Fund for the seven-day period ended December 31, 2017 was 0.01%.

Best Quarter	Worst Quarter
0.92%	0.00%
3/31/2008	12/31/2017

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns	1 Year	5 Years	10 Years
Penn Series Money Market Fund | Money Market Fund	0.01%	0.01%	0.32%

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund's financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Money Market Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  MONEY MARKET FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Money Market Fund (the “Fund”) seeks current income, while preserving capital and liquidity.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable annuity contract or variable life insurance policy (each, a “variable contract”) level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund will invest no less than 99.5% of its total assets in government securities, cash or repurchase agreements that are collateralized fully by government securities or cash.

Government securities generally are securities that are issued or guaranteed as to principal and interest by the U.S. Government or by one of its agencies or instrumentalities. Some government securities are backed by the full faith and credit of the U.S. Government. Some government securities are not backed by the full faith and credit of the U.S. Government but rather are supported by the issuer’s ability to borrow from the U.S. Treasury, by only the credit of the issuer, or by the United States in some other way. The Fund intends to operate as a “government money market fund” in compliance with Rule 2a-7 under the Investment Company Act of 1940, as amended (the “1940 Act”).

Under Rule 2a-7, the Fund may invest only in U.S. dollar-denominated securities that are determined to present minimal credit risk and meet certain other criteria, including relating to maturity, diversification, liquidity and credit quality. For example, the Fund invests in securities that generally have remaining maturities of 397 days or less and will have a dollar-weighted average portfolio maturity of 60 days or less and a dollar-weighted average life to maturity of 120 days or less. The Fund also maintains sufficient portfolio liquidity to meet reasonably foreseeable redemption requests. The Fund seeks to maintain a stable net asset value (“NAV”) of $1.00 per share and its portfolio is valued using the amortized cost method as permitted by Rule 2a-7. As a government money market fund, the Fund is not required to impose liquidity fees or redemptions gates. The Fund’s Board, however, may elect to impose such fees or gates in the future if it believes such measures are appropriate and in the best interests of the Fund and its shareholders.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Counterparty Risk.  The possibility that a party to a transaction involving the Fund may fail to meet its obligations thereby causing the Fund to lose money or the benefit of the transaction or preventing the Fund from selling or buying other securities to implement its investment strategies.

Credit Risk.  The possibility that an issuer of a debt security held by the Fund defaults on its payment obligations. While the Fund tries to minimize this risk by investing in high-quality securities, the credit quality of such securities may change rapidly in certain market environments and in response to certain market events, such as a decline in the credit quality of an issuer.

Income Risk.  The possibility that the Fund’s yield (the rate of dividends the Fund pays) may decline in the event of declining interest rates.

Interest Rate Risk.  The possibility that the prices of the Fund’s fixed income investments will decline due to rising interest rates.

Investment Risk.  You could lose money by investing in the Fund. Although the Fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so. An investment in the Fund is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency. Penn Mutual Asset Management, LLC (“PMAM” or the “Adviser”), the Fund’s sponsor, and its affiliates have no legal obligation to provide financial support to the Fund, and you should not expect that PMAM or its affiliates will provide financial support to the Fund at any time.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Redemption Risk.  The possibility that large redemptions may cause the Fund to sell its securities at inopportune times resulting in a loss to the Fund.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by the Fund if it is not obligated to do so because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause the Fund’s share price or yield to fall.

Risk Money Market Fund [Text]

rr_RiskMoneyMarketFund

Although the Fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the Fund is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Prior to May 1, 2016, the Fund invested in a diversified portfolio of high-quality money market instruments of a variety of issuers. Effective May 1, 2016, the Fund operates as a “government money market fund” and as such is limited to investing 99.5% of its total assets in government securities, cash or repurchase agreements that are collateralized fully by government securities or cash. Accordingly, the performance information below may have been different if the current investment strategy had been in effect during the period prior to the Fund’s conversion to a government money market fund. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower. The current yield of the Money Market Fund for the seven-day period ended December 31, 2017 was 0.01%.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
0.92%	0.00%
3/31/2008	12/31/2017

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Money Market Seven Day Yield, Caption [Text]

rr_MoneyMarketSevenDayYieldCaption

The current yield of the Money Market Fund for the seven-day period ended December 31, 2017 was 0.01%.

Penn Series Money Market Fund | Money Market Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.33%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.26%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.60%

^[1]

1 Year

rr_ExpenseExampleYear01

$ 61

3 Years

rr_ExpenseExampleYear03

192

5 Years

rr_ExpenseExampleYear05

335

10 Years

rr_ExpenseExampleYear10

$ 750

2008

rr_AnnualReturn2008

2.66%

2009

rr_AnnualReturn2009

0.43%

2010

rr_AnnualReturn2010

0.01%

2011

rr_AnnualReturn2011

0.01%

2012

rr_AnnualReturn2012

0.01%

2013

rr_AnnualReturn2013

0.01%

2014

rr_AnnualReturn2014

0.01%

2015

rr_AnnualReturn2015

0.01%

2016

rr_AnnualReturn2016

0.01%

2017

rr_AnnualReturn2017

0.01%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2008

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

0.92%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2017

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

none

1 Year

rr_AverageAnnualReturnYear01

0.01%

5 Years

rr_AverageAnnualReturnYear05

0.01%

10 Years

rr_AverageAnnualReturnYear10

0.32%

Money Market Seven Day Yield

rr_MoneyMarketSevenDayYield

0.01%

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund's financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Penn Series Limited Maturity Bond Fund

FUND SUMMARY:  LIMITED MATURITY BOND FUND

Investment Objective

The Limited Maturity Bond Fund (the “Fund”) seeks to maximize total return consistent with preservation of capital.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Limited Maturity Bond Fund Limited Maturity Bond Fund
Investment Advisory Fees	0.46%
Distribution (12b-1) Fees	none
Other Expenses	0.24%
Total Annual Fund Operating Expenses	0.70%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Limited Maturity Bond Fund | Limited Maturity Bond Fund | USD ($)	72	224	390	871

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 97% of the average value of its portfolio.

Principal Investment Strategy

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in short- to intermediate-term investment grade debt securities of U.S. government and corporate issuers, including mortgage-backed and asset-backed securities. Investment grade debt securities are those securities rated BBB- or higher by S&P, Baa3 or higher by Moody’s, or the equivalent by any other nationally recognized statistical rating organization (“NRSRO”), or if unrated, determined by the Adviser to be of comparable quality. The remaining assets are generally invested in other securities, including high yield securities (“junk bonds”) rated below investment grade by a NRSRO, or, if unrated, determined by the Adviser to be below investment grade, preferred and convertible securities, closed-end funds, exchange traded funds, money market securities or equities. While most assets will typically be invested in U.S. dollar-denominated bonds, the Fund may also invest in debt securities of foreign issuers, securities that are economically tied to emerging markets, and securities denominated in foreign currencies. The Fund may invest in derivative instruments, such as options, futures contracts, swap agreements, mortgage dollar rolls or forward commitments in keeping with the Fund’s objective.

The Adviser follows an actively managed, total-return oriented approach and seeks to invest in securities that are under-valued in the marketplace based on both a relative value analysis of individual securities combined with an analysis of macro-economic factors. The Adviser will purchase an individual security when doing so is also consistent with its macro-economic outlook, including its forecast of interest rates and its analysis of the yield curve (a measure of interest rates of securities with the same quality, but different maturities). The Adviser will seek to opportunistically purchase securities to take advantage of inefficiencies of prices in the securities markets, and will sell a security when it believes that the security has been fully priced. The Adviser seeks to reduce credit risk by diversifying among many issuers and different types of securities.

The average duration of this Fund normally varies within one year (plus or minus) of the duration of the Bloomberg Barclays U.S. Government/Credit 1-3 Year Bond Index, as calculated by the Adviser. The average duration of the Bloomberg Barclays U.S. Government/Credit 1-3 Year Bond Index, as of March 31, 2018, was 1.85 years. Duration measures the sensitivity of a debt security to changes in interest rates. Generally, the longer the maturity or duration of a fixed income security (or fixed income portfolio), the more sensitive it will be to interest rate changes.

The Adviser will look for inefficiencies in the market and sell when it feels a security is fully priced. As a result, portfolio turnover can be expected to be relatively high, which may result in increased transaction costs, such as commissions, and may lower fund performance.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Convertible Securities Risk.  The possibility that the value of the Fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by the Fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by the Fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by the Fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Fixed Income Market Risk.  The possibility that the market value of a fixed-income security may decline due to general market conditions that are not specifically related to a particular company, such as real or perceived adverse economic conditions, changes in the outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. Fixed income securities markets may, in response to governmental intervention, economic or market developments (including potentially a reduction in the number of broker-dealers willing to engage in market-making activity), or other factors, experience periods of increased, and sometimes unpredictable, volatility and reduced liquidity. During those periods, the Fund may experience increased levels of shareholder redemptions, and may have to sell securities at inopportune times, and at unfavorable prices. Fixed income securities also may be difficult to value during such periods. In recent periods, governmental financial regulators, including the U.S. Federal Reserve, have taken steps to maintain historically low interest rates by purchasing bonds. Steps by those regulators to curtail or “taper” such activities could result in the effects described above, and could have a material adverse effect on prices for fixed income securities and on the management of the Fund.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

High Yield Bond Risk.  The possibility that the Fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the Fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to the Fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Inflation Linked Bond Risk.  The possibility that the value of the Fund’s investments in inflation linked bonds will decline in value in response to a rise in real interest rates resulting in losses to the Fund. Inflation linked bonds may experience greater losses than other debt securities with similar durations when real interest rates rise faster than nominal interest rates.

Interest Rate Risk.  The possibility that the prices of the Fund’s fixed income investments will decline due to rising interest rates.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Mortgage- and Asset-Backed Securities Risk.  The possibility that the Fund’s investments in mortgage- and asset-backed securities may decline in value and become less liquid when defaults on the underlying mortgages or assets occur and may exhibit additional volatility in periods of rising interest rates. Rising interest rates tend to extend the duration of these securities, making them more sensitive to changes in interest rates than instruments with fixed payment schedules. When interest rates decline or are low, the prepayment of mortgages or assets underlying such securities may reduce the Fund’s returns.

Portfolio Turnover Risk.  The possibility that the Fund may frequently buy and sell portfolio securities, which may increase transaction costs to the Fund and cause the Fund’s performance to be less than you expect.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing the Fund to invest in fixed income securities with lower interest rates, which may adversely affect the Fund’s performance.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by the Fund if it is not obligated to do because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause the Fund’s share price or yield to fall.

An investment in the Fund may be appropriate for investors who are seeking the highest current income consistent with liquidity and low risk to principal available through an investment in investment grade debt.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
2.57%	-0.80%
12/31/2008	12/31/2010

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Limited Maturity Bond Fund	1 Year	5 Years	10 Years
Limited Maturity Bond Fund	1.68%	1.02%	1.85%
Bloomberg Barclays Capital U.S. Government/Credit 1-3 Year Bond Index (reflects no deduction for fees, expenses or taxes)	0.84%	0.84%	1.85%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Limited Maturity Bond Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  LIMITED MATURITY BOND FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Limited Maturity Bond Fund (the “Fund”) seeks to maximize total return consistent with preservation of capital.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 97% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

97.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in short- to intermediate-term investment grade debt securities of U.S. government and corporate issuers, including mortgage-backed and asset-backed securities. Investment grade debt securities are those securities rated BBB- or higher by S&P, Baa3 or higher by Moody’s, or the equivalent by any other nationally recognized statistical rating organization (“NRSRO”), or if unrated, determined by the Adviser to be of comparable quality. The remaining assets are generally invested in other securities, including high yield securities (“junk bonds”) rated below investment grade by a NRSRO, or, if unrated, determined by the Adviser to be below investment grade, preferred and convertible securities, closed-end funds, exchange traded funds, money market securities or equities. While most assets will typically be invested in U.S. dollar-denominated bonds, the Fund may also invest in debt securities of foreign issuers, securities that are economically tied to emerging markets, and securities denominated in foreign currencies. The Fund may invest in derivative instruments, such as options, futures contracts, swap agreements, mortgage dollar rolls or forward commitments in keeping with the Fund’s objective.

The Adviser follows an actively managed, total-return oriented approach and seeks to invest in securities that are under-valued in the marketplace based on both a relative value analysis of individual securities combined with an analysis of macro-economic factors. The Adviser will purchase an individual security when doing so is also consistent with its macro-economic outlook, including its forecast of interest rates and its analysis of the yield curve (a measure of interest rates of securities with the same quality, but different maturities). The Adviser will seek to opportunistically purchase securities to take advantage of inefficiencies of prices in the securities markets, and will sell a security when it believes that the security has been fully priced. The Adviser seeks to reduce credit risk by diversifying among many issuers and different types of securities.

The average duration of this Fund normally varies within one year (plus or minus) of the duration of the Bloomberg Barclays U.S. Government/Credit 1-3 Year Bond Index, as calculated by the Adviser. The average duration of the Bloomberg Barclays U.S. Government/Credit 1-3 Year Bond Index, as of March 31, 2018, was 1.85 years. Duration measures the sensitivity of a debt security to changes in interest rates. Generally, the longer the maturity or duration of a fixed income security (or fixed income portfolio), the more sensitive it will be to interest rate changes.

The Adviser will look for inefficiencies in the market and sell when it feels a security is fully priced. As a result, portfolio turnover can be expected to be relatively high, which may result in increased transaction costs, such as commissions, and may lower fund performance.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Convertible Securities Risk.  The possibility that the value of the Fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by the Fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by the Fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by the Fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Fixed Income Market Risk.  The possibility that the market value of a fixed-income security may decline due to general market conditions that are not specifically related to a particular company, such as real or perceived adverse economic conditions, changes in the outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. Fixed income securities markets may, in response to governmental intervention, economic or market developments (including potentially a reduction in the number of broker-dealers willing to engage in market-making activity), or other factors, experience periods of increased, and sometimes unpredictable, volatility and reduced liquidity. During those periods, the Fund may experience increased levels of shareholder redemptions, and may have to sell securities at inopportune times, and at unfavorable prices. Fixed income securities also may be difficult to value during such periods. In recent periods, governmental financial regulators, including the U.S. Federal Reserve, have taken steps to maintain historically low interest rates by purchasing bonds. Steps by those regulators to curtail or “taper” such activities could result in the effects described above, and could have a material adverse effect on prices for fixed income securities and on the management of the Fund.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

High Yield Bond Risk.  The possibility that the Fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the Fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to the Fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Inflation Linked Bond Risk.  The possibility that the value of the Fund’s investments in inflation linked bonds will decline in value in response to a rise in real interest rates resulting in losses to the Fund. Inflation linked bonds may experience greater losses than other debt securities with similar durations when real interest rates rise faster than nominal interest rates.

Interest Rate Risk.  The possibility that the prices of the Fund’s fixed income investments will decline due to rising interest rates.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Mortgage- and Asset-Backed Securities Risk.  The possibility that the Fund’s investments in mortgage- and asset-backed securities may decline in value and become less liquid when defaults on the underlying mortgages or assets occur and may exhibit additional volatility in periods of rising interest rates. Rising interest rates tend to extend the duration of these securities, making them more sensitive to changes in interest rates than instruments with fixed payment schedules. When interest rates decline or are low, the prepayment of mortgages or assets underlying such securities may reduce the Fund’s returns.

Portfolio Turnover Risk.  The possibility that the Fund may frequently buy and sell portfolio securities, which may increase transaction costs to the Fund and cause the Fund’s performance to be less than you expect.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing the Fund to invest in fixed income securities with lower interest rates, which may adversely affect the Fund’s performance.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by the Fund if it is not obligated to do because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause the Fund’s share price or yield to fall.

An investment in the Fund may be appropriate for investors who are seeking the highest current income consistent with liquidity and low risk to principal available through an investment in investment grade debt.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
2.57%	-0.80%
12/31/2008	12/31/2010

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Limited Maturity Bond Fund | Limited Maturity Bond Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.46%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.24%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.70%

1 Year

rr_ExpenseExampleYear01

$ 72

3 Years

rr_ExpenseExampleYear03

224

5 Years

rr_ExpenseExampleYear05

390

10 Years

rr_ExpenseExampleYear10

$ 871

2008

rr_AnnualReturn2008

5.03%

2009

rr_AnnualReturn2009

1.89%

2010

rr_AnnualReturn2010

3.71%

2011

rr_AnnualReturn2011

2.24%

2012

rr_AnnualReturn2012

0.61%

2013

rr_AnnualReturn2013

(0.09%)

2014

rr_AnnualReturn2014

0.17%

2015

rr_AnnualReturn2015

0.78%

2016

rr_AnnualReturn2016

2.59%

2017

rr_AnnualReturn2017

1.68%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Dec. 31, 2008

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

2.57%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2010

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(0.80%)

1 Year

rr_AverageAnnualReturnYear01

1.68%

5 Years

rr_AverageAnnualReturnYear05

1.02%

10 Years

rr_AverageAnnualReturnYear10

1.85%

Penn Series Limited Maturity Bond Fund | Bloomberg Barclays Capital U.S. Government/Credit 1-3 Year Bond Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

0.84%

5 Years

rr_AverageAnnualReturnYear05

0.84%

10 Years

rr_AverageAnnualReturnYear10

1.85%

XML

Penn Series Quality Bond Fund

FUND SUMMARY:  QUALITY BOND FUND

Investment Objective

The Quality Bond Fund (the “Fund”) seeks to maximize total return over the long term consistent with the preservation of capital.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Quality Bond Fund Quality Bond Fund
Investment Advisory Fees	0.44%
Distribution (12b-1) Fees	none
Other Expenses	0.22%
Total Annual Fund Operating Expenses	0.66%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Quality Bond Fund | Quality Bond Fund | USD ($)	67	211	368	822

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 72% of the average value of its portfolio.

Principal Investment Strategy

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in marketable investment grade debt securities, which are those securities rated BBB- or higher by S&P, Baa3 or higher by Moody’s, or the equivalent by any other nationally recognized statistical rating organization (“NRSRO”), or, if unrated, determined by the Adviser to be of comparably quality. The remaining assets are generally invested in other securities, including high yield securities (“junk bonds”) rated below investment grade by a NRSRO, or, if unrated, determined by the Adviser to be below investment grade, preferred and convertible securities, closed-end funds, exchange traded funds, money market securities or equities. While most assets will typically be invested in U.S. dollar-denominated bonds, the Fund may also invest in debt securities of foreign issuers, securities that are economically tied to emerging markets, and securities denominated in foreign currencies. The Fund may invest in derivative instruments, such as options, futures contracts, swap agreements, mortgage dollar rolls or forward commitments in keeping with the Fund’s objective.

The Adviser follows an actively managed, total-return oriented approach and seeks to find securities that are under-valued in the marketplace based on both a relative value analysis of individual securities combined with an analysis of macro-economic factors. With this approach, the Adviser attempts to identify securities that are under-valued based on their quality, maturity, and sector in the marketplace. The Adviser will purchase an individual security when doing so is also consistent with its macro-economic outlook, including its forecast of interest rates and its analysis of the yield curve (a measure of interest rates of securities with the same quality, but different maturities). In addition, the Adviser will seek to opportunistically purchase securities to take advantage of inefficiencies of prices in the securities markets. The Adviser will sell a security when it believes that the security has been fully priced. The Adviser seeks to reduce credit risk by diversifying among many issuers and different types of securities.

The average portfolio duration of this Fund normally varies within two years (plus or minus) of the duration of the Bloomberg Barclays Capital U.S. Aggregate Bond Index, as calculated by the Adviser. The average duration of the Bloomberg Barclays Capital U.S. Aggregate Bond Index, as of March 31, 2018, was 5.99 years. Duration is a measure used to determine the sensitivity of a debt security to changes in interest rates. Generally, the longer the maturity or duration of a fixed income security (or fixed income portfolio), the more sensitive it will be to interest rate changes.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Convertible Securities Risk.  The possibility that the value of the Fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by the Fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by the Fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by the Fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Fixed Income Market Risk.  The possibility that the market value of a fixed-income security may decline due to general market conditions that are not specifically related to a particular company, such as real or perceived adverse economic conditions, changes in the outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. Fixed income securities markets may, in response to governmental intervention, economic or market developments (including potentially a reduction in the number of broker-dealers willing to engage in market-making activity), or other factors, experience periods of increased, and sometimes unpredictable, volatility and reduced liquidity. During those periods, the Fund may experience increased levels of shareholder redemptions, and may have to sell securities at inopportune times, and at unfavorable prices. Fixed income securities also may be difficult to value during such periods. In recent periods, governmental financial regulators, including the U.S. Federal Reserve, have taken steps to maintain historically low interest rates by purchasing bonds. Steps by those regulators to curtail or “taper” such activities could result in the effects described above, and could have a material adverse effect on prices for fixed income securities and on the management of the Fund.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

High Yield Bond Risk.  The possibility that the Fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the Fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to the Fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Inflation Linked Bond Risk.  The possibility that the value of the Fund’s investments in inflation linked bonds will decline in value in response to a rise in real interest rates resulting in losses to the Fund. Inflation linked bonds may experience greater losses than other debt securities with similar durations when real interest rates rise faster than nominal interest rates.

Interest Rate Risk.  The possibility that the prices of the Fund’s fixed income investments will decline due to rising interest rates.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Mortgage- and Asset-Backed Securities Risk.  The possibility that the Fund’s investments in mortgage- and asset-backed securities may decline in value and become less liquid when defaults on the underlying mortgages or assets occur and may exhibit additional volatility in periods of rising interest rates. Rising interest rates tend to extend the duration of these securities, making them more sensitive to changes in interest rates than instruments with fixed payment schedules. When interest rates decline or are low, the prepayment of mortgages or assets underlying such securities may reduce the Fund’s returns.

Portfolio Turnover Risk.  The possibility that the Fund may frequently buy and sell portfolio securities, which may increase transaction costs to the Fund and cause the Fund’s performance to be less than you expect.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing the Fund to invest in fixed income securities with lower interest rates, which may adversely affect the Fund’s performance.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by the Fund if it is not obligated to do because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause the Fund’s share price or yield to fall.

An investment in the Fund may be appropriate for investors who are seeking investment income and preservation of principal.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
6.59%	-2.75%
9/30/2011	6/30/2013

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Quality Bond Fund	1 Year	5 Years	10 Years
Quality Bond Fund	4.63%	2.24%	4.14%
Bloomberg Barclays Capital U.S. Aggregate Bond Index (reflects no deduction for fees, expenses or taxes)	3.54%	2.10%	4.01%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Quality Bond Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  QUALITY BOND FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Quality Bond Fund (the “Fund”) seeks to maximize total return over the long term consistent with the preservation of capital.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 72% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

72.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in marketable investment grade debt securities, which are those securities rated BBB- or higher by S&P, Baa3 or higher by Moody’s, or the equivalent by any other nationally recognized statistical rating organization (“NRSRO”), or, if unrated, determined by the Adviser to be of comparably quality. The remaining assets are generally invested in other securities, including high yield securities (“junk bonds”) rated below investment grade by a NRSRO, or, if unrated, determined by the Adviser to be below investment grade, preferred and convertible securities, closed-end funds, exchange traded funds, money market securities or equities. While most assets will typically be invested in U.S. dollar-denominated bonds, the Fund may also invest in debt securities of foreign issuers, securities that are economically tied to emerging markets, and securities denominated in foreign currencies. The Fund may invest in derivative instruments, such as options, futures contracts, swap agreements, mortgage dollar rolls or forward commitments in keeping with the Fund’s objective.

The Adviser follows an actively managed, total-return oriented approach and seeks to find securities that are under-valued in the marketplace based on both a relative value analysis of individual securities combined with an analysis of macro-economic factors. With this approach, the Adviser attempts to identify securities that are under-valued based on their quality, maturity, and sector in the marketplace. The Adviser will purchase an individual security when doing so is also consistent with its macro-economic outlook, including its forecast of interest rates and its analysis of the yield curve (a measure of interest rates of securities with the same quality, but different maturities). In addition, the Adviser will seek to opportunistically purchase securities to take advantage of inefficiencies of prices in the securities markets. The Adviser will sell a security when it believes that the security has been fully priced. The Adviser seeks to reduce credit risk by diversifying among many issuers and different types of securities.

The average portfolio duration of this Fund normally varies within two years (plus or minus) of the duration of the Bloomberg Barclays Capital U.S. Aggregate Bond Index, as calculated by the Adviser. The average duration of the Bloomberg Barclays Capital U.S. Aggregate Bond Index, as of March 31, 2018, was 5.99 years. Duration is a measure used to determine the sensitivity of a debt security to changes in interest rates. Generally, the longer the maturity or duration of a fixed income security (or fixed income portfolio), the more sensitive it will be to interest rate changes.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Convertible Securities Risk.  The possibility that the value of the Fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by the Fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by the Fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by the Fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Fixed Income Market Risk.  The possibility that the market value of a fixed-income security may decline due to general market conditions that are not specifically related to a particular company, such as real or perceived adverse economic conditions, changes in the outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. Fixed income securities markets may, in response to governmental intervention, economic or market developments (including potentially a reduction in the number of broker-dealers willing to engage in market-making activity), or other factors, experience periods of increased, and sometimes unpredictable, volatility and reduced liquidity. During those periods, the Fund may experience increased levels of shareholder redemptions, and may have to sell securities at inopportune times, and at unfavorable prices. Fixed income securities also may be difficult to value during such periods. In recent periods, governmental financial regulators, including the U.S. Federal Reserve, have taken steps to maintain historically low interest rates by purchasing bonds. Steps by those regulators to curtail or “taper” such activities could result in the effects described above, and could have a material adverse effect on prices for fixed income securities and on the management of the Fund.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

High Yield Bond Risk.  The possibility that the Fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the Fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to the Fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Inflation Linked Bond Risk.  The possibility that the value of the Fund’s investments in inflation linked bonds will decline in value in response to a rise in real interest rates resulting in losses to the Fund. Inflation linked bonds may experience greater losses than other debt securities with similar durations when real interest rates rise faster than nominal interest rates.

Interest Rate Risk.  The possibility that the prices of the Fund’s fixed income investments will decline due to rising interest rates.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Mortgage- and Asset-Backed Securities Risk.  The possibility that the Fund’s investments in mortgage- and asset-backed securities may decline in value and become less liquid when defaults on the underlying mortgages or assets occur and may exhibit additional volatility in periods of rising interest rates. Rising interest rates tend to extend the duration of these securities, making them more sensitive to changes in interest rates than instruments with fixed payment schedules. When interest rates decline or are low, the prepayment of mortgages or assets underlying such securities may reduce the Fund’s returns.

Portfolio Turnover Risk.  The possibility that the Fund may frequently buy and sell portfolio securities, which may increase transaction costs to the Fund and cause the Fund’s performance to be less than you expect.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing the Fund to invest in fixed income securities with lower interest rates, which may adversely affect the Fund’s performance.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by the Fund if it is not obligated to do because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause the Fund’s share price or yield to fall.

An investment in the Fund may be appropriate for investors who are seeking investment income and preservation of principal.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
6.59%	-2.75%
9/30/2011	6/30/2013

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Quality Bond Fund | Quality Bond Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.44%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.22%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.66%

1 Year

rr_ExpenseExampleYear01

$ 67

3 Years

rr_ExpenseExampleYear03

211

5 Years

rr_ExpenseExampleYear05

368

10 Years

rr_ExpenseExampleYear10

$ 822

2008

rr_AnnualReturn2008

5.10%

2009

rr_AnnualReturn2009

6.02%

2010

rr_AnnualReturn2010

6.06%

2011

rr_AnnualReturn2011

10.12%

2012

rr_AnnualReturn2012

3.22%

2013

rr_AnnualReturn2013

(2.97%)

2014

rr_AnnualReturn2014

5.10%

2015

rr_AnnualReturn2015

0.37%

2016

rr_AnnualReturn2016

4.31%

2017

rr_AnnualReturn2017

4.63%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2011

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

6.59%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Jun. 30, 2013

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(2.75%)

1 Year

rr_AverageAnnualReturnYear01

4.63%

5 Years

rr_AverageAnnualReturnYear05

2.24%

10 Years

rr_AverageAnnualReturnYear10

4.14%

Penn Series Quality Bond Fund | Bloomberg Barclays Capital U.S. Aggregate Bond Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

3.54%

5 Years

rr_AverageAnnualReturnYear05

2.10%

10 Years

rr_AverageAnnualReturnYear10

4.01%

XML

Penn Series High Yield Bond Fund

FUND SUMMARY:  HIGH YIELD BOND FUND

Investment Objective

The investment objective of the High Yield Bond Fund (the “Fund”) is to realize high current income.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series High Yield Bond Fund High Yield Bond Fund
Investment Advisory Fees	0.46%
Distribution (12b-1) Fees	none
Other Expenses	0.30%
Acquired Fund Fees and Expenses	0.02%
Total Annual Fund Operating Expenses	0.78%	[1],[2]

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series High Yield Bond Fund | High Yield Bond Fund | USD ($)	80	249	433	966

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 78% of the average value of its portfolio.

Principal Investment Strategy

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in a widely diversified portfolio of high yield corporate bonds (commonly known as “junk bonds”), income-producing convertible securities and preferred stocks that are rated below investment grade or not rated by any major credit rating agency but deemed to be below investment grade by the Adviser. High yield bonds are rated below investment grade (BB and lower, or an equivalent rating), and tend to provide high income in an effort to compensate investors for their higher risk of default, which is the failure to make required interest or principal payments. High yield bond issuers include small or relatively new companies lacking the history or capital to merit investment grade status, former blue-chip companies downgraded because of financial problems, companies electing to borrow heavily to finance or avoid a takeover or buyout, and firms with heavy debt loads.

The Fund’s dollar-weighted average maturity generally is expected to be in the five- to ten-year range, but will vary with market conditions. In selecting investments for the Fund, the Adviser relies extensively on its credit research analysts. The Fund intends to focus primarily on the higher-quality range (BB and B, or an equivalent rating) of the high yield market.

While most assets will typically be invested in U.S. dollar-denominated bonds, the Fund may also invest in bonds of foreign issuers as well as use forward currency exchange contracts and credit default swaps in keeping with the Fund’s objectives. Forward currency exchange contracts would typically be used to protect the Fund’s foreign bond holdings from adverse currency movements relative to the U.S. dollar and credit default swaps would typically be used to protect the value of certain portfolio holdings or to manage the Fund’s overall exposure to changes in credit quality.

The Fund may sell holdings for a variety of reasons, such as to adjust a portfolio’s average maturity or credit quality, or to shift assets into and out of higher-yielding securities, or to reduce exposure to certain securities.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Bank Loans Risk.  The possibility that, to the extent the Fund invests in bank loans, it is exposed to additional risks beyond those associated with traditional debt securities, including liquidity risk, prepayment risk, extension risk, the risk of subordination to other creditors, restrictions on resale, and the lack of a regular trading market and publicly available information. In addition, liquidity risk may be more pronounced for a portfolio investing in loans because certain loans may have a more limited secondary market. These loans may be difficult to value, which may result in a loss. In addition, bank loans generally are subject to extended settlement periods in excess of seven days, which may impair the Fund’s ability to sell or realize the full value of its loans in the event of a need to liquidate such loans. Purchases and sales of loans in the secondary market generally are subject to contractual restrictions that may delay the Fund’s ability to make timely redemptions. Bank loans may not be considered securities and, therefore, the Fund may not have the protections of the federal securities laws with respect to its holdings of such loans.

Convertible Securities Risk.  The possibility that the value of the Fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by the Fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by the Fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by the Fund defaults on its payment obligations.

Credit Default Swap Risk.  The possibility that the Fund’s investments in credit default swaps may subject the Fund to greater risks than if the Fund were to invest directly in the reference obligation. Investing in credit default swaps exposes the Fund to the credit risk of both the counterparty to the credit default swap and the issuer of the underlying reference obligation. The Fund could realize a loss on its investment if it does not correctly evaluate the creditworthiness of the issuer of the bond or other reference obligation on which the credit default swap is based, as well as the continued creditworthiness of the counterparty. Investments in credit default swaps are also subject to liquidity risk.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Fixed Income Market Risk.  The possibility that the market value of a fixed-income security may decline due to general market conditions that are not specifically related to a particular company, such as real or perceived adverse economic conditions, changes in the outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. Fixed income securities markets may, in response to governmental intervention, economic or market developments (including potentially a reduction in the number of broker-dealers willing to engage in market-making activity), or other factors, experience periods of increased, and sometimes unpredictable, volatility and reduced liquidity. During those periods, the Fund may experience increased levels of shareholder redemptions, and may have to sell securities at inopportune times, and at unfavorable prices. Fixed income securities also may be difficult to value during such periods. In recent periods, governmental financial regulators, including the U.S. Federal Reserve, have taken steps to maintain historically low interest rates by purchasing bonds. Steps by those regulators to curtail or “taper” such activities could result in the effects described above, and could have a material adverse effect on prices for fixed income securities and on the management of the Fund.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

High Yield Bond Risk.  The possibility that the Fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the Fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to the Fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Interest Rate Risk.  The possibility that the prices of the Fund’s fixed income investments will decline due to rising interest rates.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Preferred Stock Risk.  The possibility that the value of the Fund’s investments in preferred stock may decline if stock prices fall or interest rates rise. In the event of a liquidation, the rights of a company’s preferred stock to the distribution of company assets are generally subordinate to the rights of a company’s debt securities.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing the Fund to invest in fixed income securities with lower interest rates, which may adversely affect the Fund’s performance.

An investment in the Fund may be appropriate for long-term, risk-oriented investors who are willing to accept the greater risks and uncertainties of investing in high yield bonds in the hope of earning high current income.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Performance shown reflects the Fund’s investment performance when managed by a previous sub-adviser pursuant to a substantially similar principal investment strategy. Effective May 1, 2018, Penn Mutual Asset Management, LLC assumed responsibility for the Fund’s day-to-day portfolio management and the Fund is no longer sub-advised by T. Rowe Price Associates, Inc. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
18.08%	-17.56%
6/30/2009	12/31/2008

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series High Yield Bond Fund	1 Year	5 Years	10 Years
High Yield Bond Fund	7.42%	5.70%	7.07%
CSFB High Yield Bond Index (reflects no deduction for fees, expenses or taxes)	7.03%	5.68%	7.58%

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund's financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

[2] The expense information in this fee table has been restated to reflect a reduction in the Fund's Investment Advisory Fee rate, effective May 1, 2018. As such, the Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratio in the Fund's financial highlights and financial statements, which reflect the prior Investment Advisory Fee rate.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series High Yield Bond Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  HIGH YIELD BOND FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the High Yield Bond Fund (the “Fund”) is to realize high current income.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 78% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

78.00%

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

The expense information in this fee table has been restated to reflect a reduction in the Fund’s Investment Advisory Fee rate, effective May 1, 2018.

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in a widely diversified portfolio of high yield corporate bonds (commonly known as “junk bonds”), income-producing convertible securities and preferred stocks that are rated below investment grade or not rated by any major credit rating agency but deemed to be below investment grade by the Adviser. High yield bonds are rated below investment grade (BB and lower, or an equivalent rating), and tend to provide high income in an effort to compensate investors for their higher risk of default, which is the failure to make required interest or principal payments. High yield bond issuers include small or relatively new companies lacking the history or capital to merit investment grade status, former blue-chip companies downgraded because of financial problems, companies electing to borrow heavily to finance or avoid a takeover or buyout, and firms with heavy debt loads.

The Fund’s dollar-weighted average maturity generally is expected to be in the five- to ten-year range, but will vary with market conditions. In selecting investments for the Fund, the Adviser relies extensively on its credit research analysts. The Fund intends to focus primarily on the higher-quality range (BB and B, or an equivalent rating) of the high yield market.

While most assets will typically be invested in U.S. dollar-denominated bonds, the Fund may also invest in bonds of foreign issuers as well as use forward currency exchange contracts and credit default swaps in keeping with the Fund’s objectives. Forward currency exchange contracts would typically be used to protect the Fund’s foreign bond holdings from adverse currency movements relative to the U.S. dollar and credit default swaps would typically be used to protect the value of certain portfolio holdings or to manage the Fund’s overall exposure to changes in credit quality.

The Fund may sell holdings for a variety of reasons, such as to adjust a portfolio’s average maturity or credit quality, or to shift assets into and out of higher-yielding securities, or to reduce exposure to certain securities.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Bank Loans Risk.  The possibility that, to the extent the Fund invests in bank loans, it is exposed to additional risks beyond those associated with traditional debt securities, including liquidity risk, prepayment risk, extension risk, the risk of subordination to other creditors, restrictions on resale, and the lack of a regular trading market and publicly available information. In addition, liquidity risk may be more pronounced for a portfolio investing in loans because certain loans may have a more limited secondary market. These loans may be difficult to value, which may result in a loss. In addition, bank loans generally are subject to extended settlement periods in excess of seven days, which may impair the Fund’s ability to sell or realize the full value of its loans in the event of a need to liquidate such loans. Purchases and sales of loans in the secondary market generally are subject to contractual restrictions that may delay the Fund’s ability to make timely redemptions. Bank loans may not be considered securities and, therefore, the Fund may not have the protections of the federal securities laws with respect to its holdings of such loans.

Convertible Securities Risk.  The possibility that the value of the Fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by the Fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by the Fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by the Fund defaults on its payment obligations.

Credit Default Swap Risk.  The possibility that the Fund’s investments in credit default swaps may subject the Fund to greater risks than if the Fund were to invest directly in the reference obligation. Investing in credit default swaps exposes the Fund to the credit risk of both the counterparty to the credit default swap and the issuer of the underlying reference obligation. The Fund could realize a loss on its investment if it does not correctly evaluate the creditworthiness of the issuer of the bond or other reference obligation on which the credit default swap is based, as well as the continued creditworthiness of the counterparty. Investments in credit default swaps are also subject to liquidity risk.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Fixed Income Market Risk.  The possibility that the market value of a fixed-income security may decline due to general market conditions that are not specifically related to a particular company, such as real or perceived adverse economic conditions, changes in the outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. Fixed income securities markets may, in response to governmental intervention, economic or market developments (including potentially a reduction in the number of broker-dealers willing to engage in market-making activity), or other factors, experience periods of increased, and sometimes unpredictable, volatility and reduced liquidity. During those periods, the Fund may experience increased levels of shareholder redemptions, and may have to sell securities at inopportune times, and at unfavorable prices. Fixed income securities also may be difficult to value during such periods. In recent periods, governmental financial regulators, including the U.S. Federal Reserve, have taken steps to maintain historically low interest rates by purchasing bonds. Steps by those regulators to curtail or “taper” such activities could result in the effects described above, and could have a material adverse effect on prices for fixed income securities and on the management of the Fund.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

High Yield Bond Risk.  The possibility that the Fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the Fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to the Fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Interest Rate Risk.  The possibility that the prices of the Fund’s fixed income investments will decline due to rising interest rates.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Preferred Stock Risk.  The possibility that the value of the Fund’s investments in preferred stock may decline if stock prices fall or interest rates rise. In the event of a liquidation, the rights of a company’s preferred stock to the distribution of company assets are generally subordinate to the rights of a company’s debt securities.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing the Fund to invest in fixed income securities with lower interest rates, which may adversely affect the Fund’s performance.

An investment in the Fund may be appropriate for long-term, risk-oriented investors who are willing to accept the greater risks and uncertainties of investing in high yield bonds in the hope of earning high current income.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Performance shown reflects the Fund’s investment performance when managed by a previous sub-adviser pursuant to a substantially similar principal investment strategy. Effective May 1, 2018, Penn Mutual Asset Management, LLC assumed responsibility for the Fund’s day-to-day portfolio management and the Fund is no longer sub-advised by T. Rowe Price Associates, Inc. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
18.08%	-17.56%
6/30/2009	12/31/2008

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series High Yield Bond Fund | High Yield Bond Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.46%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.30%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.78%

^[1],[2]

1 Year

rr_ExpenseExampleYear01

$ 80

3 Years

rr_ExpenseExampleYear03

249

5 Years

rr_ExpenseExampleYear05

433

10 Years

rr_ExpenseExampleYear10

$ 966

2008

rr_AnnualReturn2008

(23.98%)

2009

rr_AnnualReturn2009

46.44%

2010

rr_AnnualReturn2010

14.17%

2011

rr_AnnualReturn2011

3.07%

2012

rr_AnnualReturn2012

14.56%

2013

rr_AnnualReturn2013

7.91%

2014

rr_AnnualReturn2014

1.86%

2015

rr_AnnualReturn2015

(3.37%)

2016

rr_AnnualReturn2016

15.83%

2017

rr_AnnualReturn2017

7.42%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

18.08%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(17.56%)

1 Year

rr_AverageAnnualReturnYear01

7.42%

5 Years

rr_AverageAnnualReturnYear05

5.70%

10 Years

rr_AverageAnnualReturnYear10

7.07%

Penn Series High Yield Bond Fund | CSFB High Yield Bond Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

7.03%

5 Years

rr_AverageAnnualReturnYear05

5.68%

10 Years

rr_AverageAnnualReturnYear10

7.58%

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund's financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

[2] The expense information in this fee table has been restated to reflect a reduction in the Fund's Investment Advisory Fee rate, effective May 1, 2018. As such, the Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratio in the Fund's financial highlights and financial statements, which reflect the prior Investment Advisory Fee rate.

XML

Penn Series Flexibly Managed Fund

FUND SUMMARY:  FLEXIBLY MANAGED FUND

Investment Objective

The investment objective of the Flexibly Managed Fund (the “Fund”) is to maximize total return (capital appreciation and income).

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Flexibly Managed Fund Flexibly Managed Fund
Investment Advisory Fees	0.70%
Distribution (12b-1) Fees	none
Other Expenses	0.19%
Acquired Fund Fees and Expenses	0.05%
Total Annual Fund Operating Expenses	0.94%	[1]

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Flexibly Managed Fund | Flexibly Managed Fund | USD ($)	96	300	520	1,155

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 61% of the average value of its portfolio.

Principal Investment Strategy

The Fund normally invests at least 50% of its total assets in stocks of established U.S. companies that it believes have above-average potential for capital growth. The Fund’s investments in stocks are primarily those issued by large capitalization companies, and stocks typically constitute at least half of total assets. The remaining assets are generally invested in other securities, such as convertibles, corporate and government debt securities (including mortgage- and asset-backed securities), high yield securities (commonly known as “junk bonds”), bank loans and foreign securities, in keeping with the Fund’s objective. The Fund’s investments in stocks generally fall into one of two categories. The larger category comprises long-term core holdings that the Sub-Adviser considers to be underpriced in terms of company assets, earnings, or other factors at the time they are purchased. The smaller category comprises opportunistic investments whose prices the Sub-Adviser expects to rise in the short term, but not necessarily over the long term. There are no limits on the market capitalization of issuers of the stocks in which the Fund invests. Since the Sub-Adviser attempts to prevent losses as well as achieve gains, it typically uses a “value approach” in selecting investments. Its in-house research team seeks to identify companies that seem under-valued by various measures, such as price/book value, and may be temporarily out of favor but have good prospects for capital appreciation. The Sub-Adviser may establish relatively large positions in companies it finds particularly attractive. The Fund may also, to a limited extent, invest in options and could write (i.e., sell) call options, primarily in an effort to protect against downside risk or to generate additional income.

The Fund may sell securities for a variety of reasons, such as to secure gains, limit losses, or redeploy assets into more promising opportunities.

The Sub-Adviser works as hard to reduce risk as to maximize gains and may realize gains rather than lose them in market declines. In addition, the Sub-Adviser searches for attractive risk/reward values among all types of securities. The portion of the Fund invested in a particular type of security, such as common stocks, results largely from case-by-case investment decisions, and the size of the Fund’s cash reserve may reflect the Sub-Adviser’s ability to find companies that meet valuation criteria rather than its market outlook. Bonds, bank loans and convertible securities may be purchased to gain additional exposure to a company or for their income or other features. Maturity and quality are not necessarily major considerations. There are no specified limits on the maturities or credit ratings of the debt instruments in which the Fund invests. The Fund expects to invest more than 25% of its net assets in the banking industry when the Fund’s position in issues maturing in one year or less equals 35% or more of the Fund’s total assets. The Fund may invest up to 25% of its total assets in below-investment grade securities. There is no limit on the Fund’s investments in convertible securities. The Fund may sell securities for a variety of reasons, such as to secure gains, limit losses, or redeploy assets into more promising opportunities.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Bank Loans Risk.  The possibility that, to the extent the Fund invests in bank loans, it is exposed to additional risks beyond those associated with traditional debt securities, including liquidity risk, prepayment risk, extension risk, the risk of subordination to other creditors, restrictions on resale, and the lack of a regular trading market and publicly available information. In addition, liquidity risk may be more pronounced for a portfolio investing in loans because certain loans may have a more limited secondary market. These loans may be difficult to value, which may result in a loss. In addition, bank loans generally are subject to extended settlement periods in excess of seven days, which may impair the Fund’s ability to sell or realize the full value of its loans in the event of a need to liquidate such loans. Purchases and sales of loans in the secondary market generally are subject to contractual restrictions that may delay the Fund’s ability to make timely redemptions. Bank loans may not be considered securities and, therefore, the Fund may not have the protections of the federal securities laws with respect to its holdings of such loans.

Banking Industry Risk.  The possibility that the Fund’s investments in securities in the banking industry may be adversely affected by interest rate risk, credit risk, and financial, economic, and regulatory developments affecting the banking industry, such as deteriorating economic and business conditions that cause defaults on bank loans and declines in total deposits. Banks are subject to extensive government regulation that may affect the scope of their activities, their profitability, the prices they charge and the amount of capital they maintain.

Convertible Securities Risk.  The possibility that the value of the Fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by the Fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by the Fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by the Fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Fixed Income Market Risk.  The possibility that the market value of a fixed-income security may decline due to general market conditions that are not specifically related to a particular company, such as real or perceived adverse economic conditions, changes in the outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. Fixed income securities markets may, in response to governmental intervention, economic or market developments (including potentially a reduction in the number of broker-dealers willing to engage in market-making activity), or other factors, experience periods of increased, and sometimes unpredictable, volatility and reduced liquidity. During those periods, the Fund may experience increased levels of shareholder redemptions, and may have to sell securities at inopportune times, and at unfavorable prices. Fixed income securities also may be difficult to value during such periods. In recent periods, governmental financial regulators, including the U.S. Federal Reserve, have taken steps to maintain historically low interest rates by purchasing bonds. Steps by those regulators to curtail or “taper” such activities could result in the effects described above, and could have a material adverse effect on prices for fixed income securities and on the management of the Fund.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

High Yield Bond Risk.  The possibility that the Fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the Fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to the Fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Interest Rate Risk.  The possibility that the prices of the Fund’s fixed income investments will decline due to rising interest rates.

Large-Cap Securities Risk.  The possibility that the Fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Mortgage- and Asset-Backed Securities Risk.  The possibility that the Fund’s investments in mortgage- and asset-backed securities may decline in value and become less liquid when defaults on the underlying mortgages or assets occur and may exhibit additional volatility in periods of rising interest rates. Rising interest rates tend to extend the duration of these securities, making them more sensitive to changes in interest rates than instruments with fixed payment schedules. When interest rates decline or are low, the prepayment of mortgages or assets underlying such securities may reduce the Fund’s returns.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing the Fund to invest in fixed income securities with lower interest rates, which may adversely affect the Fund’s performance.

Small- and Mid-Cap Securities Risk.  The possibility that the Fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and the Fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by the Fund if it is not obligated to do because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause the Fund’s share price or yield to fall.

“Value” Investing Risk.  The possibility that the Fund’s investments in securities believed by the Sub-Adviser to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which the Fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the Fund’s investment style shifts out of favor.

An investment in the Fund may be appropriate for investors who are seeking a relatively conservative approach to investing for total return and are willing to accept the risks and uncertainties of investing in common stocks and bonds.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
18.67%	-19.44%
6/30/2009	12/31/2008

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Flexibly Managed Fund	1 Year	5 Years	10 Years
Flexibly Managed Fund	15.12%	12.36%	8.75%
S&P 500® Index (reflects no deduction for fees, expenses or taxes)	21.83%	15.79%	8.50%

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Flexibly Managed Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  FLEXIBLY MANAGED FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Flexibly Managed Fund (the “Fund”) is to maximize total return (capital appreciation and income).

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 61% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

61.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund normally invests at least 50% of its total assets in stocks of established U.S. companies that it believes have above-average potential for capital growth. The Fund’s investments in stocks are primarily those issued by large capitalization companies, and stocks typically constitute at least half of total assets. The remaining assets are generally invested in other securities, such as convertibles, corporate and government debt securities (including mortgage- and asset-backed securities), high yield securities (commonly known as “junk bonds”), bank loans and foreign securities, in keeping with the Fund’s objective. The Fund’s investments in stocks generally fall into one of two categories. The larger category comprises long-term core holdings that the Sub-Adviser considers to be underpriced in terms of company assets, earnings, or other factors at the time they are purchased. The smaller category comprises opportunistic investments whose prices the Sub-Adviser expects to rise in the short term, but not necessarily over the long term. There are no limits on the market capitalization of issuers of the stocks in which the Fund invests. Since the Sub-Adviser attempts to prevent losses as well as achieve gains, it typically uses a “value approach” in selecting investments. Its in-house research team seeks to identify companies that seem under-valued by various measures, such as price/book value, and may be temporarily out of favor but have good prospects for capital appreciation. The Sub-Adviser may establish relatively large positions in companies it finds particularly attractive. The Fund may also, to a limited extent, invest in options and could write (i.e., sell) call options, primarily in an effort to protect against downside risk or to generate additional income.

The Fund may sell securities for a variety of reasons, such as to secure gains, limit losses, or redeploy assets into more promising opportunities.

The Sub-Adviser works as hard to reduce risk as to maximize gains and may realize gains rather than lose them in market declines. In addition, the Sub-Adviser searches for attractive risk/reward values among all types of securities. The portion of the Fund invested in a particular type of security, such as common stocks, results largely from case-by-case investment decisions, and the size of the Fund’s cash reserve may reflect the Sub-Adviser’s ability to find companies that meet valuation criteria rather than its market outlook. Bonds, bank loans and convertible securities may be purchased to gain additional exposure to a company or for their income or other features. Maturity and quality are not necessarily major considerations. There are no specified limits on the maturities or credit ratings of the debt instruments in which the Fund invests. The Fund expects to invest more than 25% of its net assets in the banking industry when the Fund’s position in issues maturing in one year or less equals 35% or more of the Fund’s total assets. The Fund may invest up to 25% of its total assets in below-investment grade securities. There is no limit on the Fund’s investments in convertible securities. The Fund may sell securities for a variety of reasons, such as to secure gains, limit losses, or redeploy assets into more promising opportunities.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund expects to invest more than 25% of its net assets in the banking industry when the Fund’s position in issues maturing in one year or less equals 35% or more of the Fund’s total assets.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Bank Loans Risk.  The possibility that, to the extent the Fund invests in bank loans, it is exposed to additional risks beyond those associated with traditional debt securities, including liquidity risk, prepayment risk, extension risk, the risk of subordination to other creditors, restrictions on resale, and the lack of a regular trading market and publicly available information. In addition, liquidity risk may be more pronounced for a portfolio investing in loans because certain loans may have a more limited secondary market. These loans may be difficult to value, which may result in a loss. In addition, bank loans generally are subject to extended settlement periods in excess of seven days, which may impair the Fund’s ability to sell or realize the full value of its loans in the event of a need to liquidate such loans. Purchases and sales of loans in the secondary market generally are subject to contractual restrictions that may delay the Fund’s ability to make timely redemptions. Bank loans may not be considered securities and, therefore, the Fund may not have the protections of the federal securities laws with respect to its holdings of such loans.

Banking Industry Risk.  The possibility that the Fund’s investments in securities in the banking industry may be adversely affected by interest rate risk, credit risk, and financial, economic, and regulatory developments affecting the banking industry, such as deteriorating economic and business conditions that cause defaults on bank loans and declines in total deposits. Banks are subject to extensive government regulation that may affect the scope of their activities, their profitability, the prices they charge and the amount of capital they maintain.

Convertible Securities Risk.  The possibility that the value of the Fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by the Fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by the Fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by the Fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Fixed Income Market Risk.  The possibility that the market value of a fixed-income security may decline due to general market conditions that are not specifically related to a particular company, such as real or perceived adverse economic conditions, changes in the outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. Fixed income securities markets may, in response to governmental intervention, economic or market developments (including potentially a reduction in the number of broker-dealers willing to engage in market-making activity), or other factors, experience periods of increased, and sometimes unpredictable, volatility and reduced liquidity. During those periods, the Fund may experience increased levels of shareholder redemptions, and may have to sell securities at inopportune times, and at unfavorable prices. Fixed income securities also may be difficult to value during such periods. In recent periods, governmental financial regulators, including the U.S. Federal Reserve, have taken steps to maintain historically low interest rates by purchasing bonds. Steps by those regulators to curtail or “taper” such activities could result in the effects described above, and could have a material adverse effect on prices for fixed income securities and on the management of the Fund.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

High Yield Bond Risk.  The possibility that the Fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the Fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to the Fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Interest Rate Risk.  The possibility that the prices of the Fund’s fixed income investments will decline due to rising interest rates.

Large-Cap Securities Risk.  The possibility that the Fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Mortgage- and Asset-Backed Securities Risk.  The possibility that the Fund’s investments in mortgage- and asset-backed securities may decline in value and become less liquid when defaults on the underlying mortgages or assets occur and may exhibit additional volatility in periods of rising interest rates. Rising interest rates tend to extend the duration of these securities, making them more sensitive to changes in interest rates than instruments with fixed payment schedules. When interest rates decline or are low, the prepayment of mortgages or assets underlying such securities may reduce the Fund’s returns.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing the Fund to invest in fixed income securities with lower interest rates, which may adversely affect the Fund’s performance.

Small- and Mid-Cap Securities Risk.  The possibility that the Fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and the Fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by the Fund if it is not obligated to do because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause the Fund’s share price or yield to fall.

“Value” Investing Risk.  The possibility that the Fund’s investments in securities believed by the Sub-Adviser to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which the Fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the Fund’s investment style shifts out of favor.

An investment in the Fund may be appropriate for investors who are seeking a relatively conservative approach to investing for total return and are willing to accept the risks and uncertainties of investing in common stocks and bonds.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
18.67%	-19.44%
6/30/2009	12/31/2008

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Flexibly Managed Fund | Flexibly Managed Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.70%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.19%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.05%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.94%

^[1]

1 Year

rr_ExpenseExampleYear01

$ 96

3 Years

rr_ExpenseExampleYear03

300

5 Years

rr_ExpenseExampleYear05

520

10 Years

rr_ExpenseExampleYear10

$ 1,155

2008

rr_AnnualReturn2008

(27.83%)

2009

rr_AnnualReturn2009

32.92%

2010

rr_AnnualReturn2010

13.92%

2011

rr_AnnualReturn2011

3.04%

2012

rr_AnnualReturn2012

14.77%

2013

rr_AnnualReturn2013

25.25%

2014

rr_AnnualReturn2014

12.09%

2015

rr_AnnualReturn2015

5.02%

2016

rr_AnnualReturn2016

8.06%

2017

rr_AnnualReturn2017

15.12%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

18.67%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(19.44%)

1 Year

rr_AverageAnnualReturnYear01

15.12%

5 Years

rr_AverageAnnualReturnYear05

12.36%

10 Years

rr_AverageAnnualReturnYear10

8.75%

Penn Series Flexibly Managed Fund | S&P 500® Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

21.83%

5 Years

rr_AverageAnnualReturnYear05

15.79%

10 Years

rr_AverageAnnualReturnYear10

8.50%

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Penn Series Balanced Fund

FUND SUMMARY:  BALANCED FUND

Investment Objective

The investment objective of the Balanced Fund (the “Fund”) is to seek long-term growth and current income.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Balanced Fund Balanced Fund
Investment Advisory Fees	none
Distribution (12b-1) Fees	none
Other Expenses	0.19%
Acquired Fund Fees and Expenses	0.48%
Total Annual Fund Operating Expenses	0.67%	[1]

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Balanced Fund | Balanced Fund | USD ($)	68	214	373	835

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 9% of the average value of its portfolio.

Principal Investment Strategy

The Fund seeks to achieve its investment objective by using a “fund-of-funds” strategy. Accordingly, the Fund invests in a combination of other Penn Series Funds (each, an “underlying fund” and, collectively, the “underlying funds”) in accordance with its target asset allocation. These underlying funds invest their assets directly in equity, fixed income, money market and other securities in accordance with their own investment objectives and policies. The underlying funds are managed using both indexed and active management strategies. The Fund intends to invest primarily in a combination of underlying funds; however, the Fund may invest directly in equity and fixed income securities and cash equivalents, including money market securities.

Under normal circumstances, the Fund will invest 50%-70% of its assets in stock and other equity underlying funds, 30%-50% of its assets in bond and other fixed income funds, and 0%-20% of its assets in money market funds. The Fund’s allocation strategy is designed to provide a mix of the growth opportunities of stock investing with the income opportunities of bonds and other fixed income securities.

The Fund’s underlying equity fund allocation will primarily track the performance of the large capitalization company portion of the U.S. stock market. The Fund’s underlying fixed income fund allocation will be invested primarily in a broad range of investment grade fixed income securities (although up to 10% of the underlying fund may be invested in non-investment grade securities (commonly known as “junk bonds”)), and is intended to provide results consistent with the broad U.S. fixed income market.

The following chart shows the Fund’s target asset allocation among the various asset classes. The Adviser may permit modest deviations from the target asset allocations listed below. Market appreciation or depreciation may cause the Fund to be outside of its target asset allocation range. In addition, differences in the performance of the underlying funds and the size and frequency of purchase and redemption orders may affect the Fund’s actual allocations. Accordingly, the Fund’s actual allocations may differ from this illustration.

Asset Classes and Underlying Funds	Target Asset Allocation
Equity Fund	50% - 70%
Penn Series Index 500 Fund
Fixed Income Fund	30% - 50%
Penn Series Quality Bond Fund
Money Market Fund	0% - 20%
Penn Series Money Market Fund

The Fund’s investment performance is directly related to the investment performance of the underlying funds. A brief description of each underlying fund’s principal investment strategy is provided below.

Underlying Funds	Investment Objective and Principal Investment Strategy
Penn Series Index 500 Fund	Seeks a total return (capital appreciation and income) which corresponds to that of the S&P 500® Index. Under normal circumstances, the Fund intends to invest substantially all of its assets in securities of companies included in the Index and close substitutes (such as index futures contracts) that are designed to track the S&P 500® Index.
Penn Series Quality Bond Fund	Seeks to maximize total return over the long term consistent with the preservation of capital. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in marketable investment grade debt securities.
Penn Series Money Market Fund	Seeks current income, while preserving capital and liquidity. The Fund is a government money market and will invest no less than 99.5% of its total assets in government securities, cash or repurchase agreements that are collateralized fully by government securities or cash.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Asset Allocation Risk.  The possibility that the Fund may underperform other funds with similar investment objectives due to the Fund’s allocation of assets to underlying funds investing in asset classes or market sectors that perform poorly relative to other asset categories.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Underlying Fund Investment Risk.  The possibility that the underperformance of an underlying fund may contribute to the underperformance of the Fund. The Fund’s performance and risks will be directly related to the performance and risks of the underlying funds in which it invests. In addition, the Fund indirectly pays a pro rata portion of the expenses incurred by the underlying funds, which also may lower the Fund’s performance.

Concentration Risk.  The possibility that, to the extent an underlying fund invests to a significant extent in a particular industry or group of industries within a particular sector, the underlying fund may be subject to greater risks than if its investments were broadly diversified across industries and sectors. The underlying fund also is subject to loss due to adverse occurrences that may affect that industry or group of industries.

Convertible Securities Risk.  The possibility that the value of an underlying fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by an underlying fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by an underlying fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Counterparty Risk.  The possibility that a party to a transaction involving an underlying fund may fail to meet its obligations thereby causing the underlying fund to lose money or the benefit of the transaction or preventing the underlying fund from selling or buying other securities to implement its investment strategies.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by an underlying fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of an underlying fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that an underlying fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Adviser or Sub-Adviser of the underlying fund believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Fixed Income Market Risk.  The possibility that the market value of a fixed-income security may decline due to general market conditions that are not specifically related to a particular company, such as real or perceived adverse economic conditions, changes in the outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. Fixed income securities markets may, in response to governmental intervention, economic or market developments (including potentially a reduction in the number of broker-dealers willing to engage in market-making activity), or other factors, experience periods of increased, and sometimes unpredictable, volatility and reduced liquidity. During those periods, an underlying fund may experience increased levels of shareholder redemptions, and may have to sell securities at inopportune times, and at unfavorable prices. Fixed income securities also may be difficult to value during such periods. In recent periods, governmental financial regulators, including the U.S. Federal Reserve, have taken steps to maintain historically low interest rates by purchasing bonds. Steps by those regulators to curtail or “taper” such activities could result in the effects described above, and could have a material adverse effect on prices for fixed income securities and on the management of an underlying fund.

Foreign Investment Risk.  The possibility that an underlying fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

High Yield Bond Risk.  The possibility that an underlying fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the underlying fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to an underlying fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Income Risk.  The possibility that an underlying fund’s yield (the rate of dividends the underlying fund pays) may decline in the event of declining interest rates.

Inflation Linked Bond Risk.  The possibility that the value of an underlying fund’s investments in inflation linked bonds will decline in value in response to a rise in real interest rates resulting in losses to the underlying fund. Inflation linked bonds may experience greater losses than other debt securities with similar durations when real interest rates rise faster than nominal interest rates.

Interest Rate Risk.  The possibility that the prices of an underlying fund’s fixed income investments will decline due to rising interest rates.

Investment Risk.  You may lose money by investing in the Money Market Fund. Although the Money Market Fund seeks to preserve the value of your investment at $1.00 per share, there is no guarantee that the Money Market Fund will be able to do so. An investment in the Money Market Fund is not insured or guaranteed by the FDIC or any other government agency. PMAM, the Fund’s sponsor, and its affiliates have no legal obligation to provide financial support to the Money Market Fund, and you should not expect that PMAM or its affiliates will provide financial support to the Money Market Fund at any time.

Large-Cap Securities Risk.  The possibility that an underlying fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of an underlying fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If an underlying fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Mortgage- and Asset-Backed Securities Risk.  The possibility that an underlying fund’s investments in mortgage- and asset-backed securities may decline in value and become less liquid when defaults on the underlying mortgages or assets occur and may exhibit additional volatility in periods of rising interest rates. Rising interest rates tend to extend the duration of these securities, making them more sensitive to changes in interest rates than instruments with fixed payment schedules. When interest rates decline or are low, the prepayment of mortgages or assets underlying such securities may reduce the underlying fund’s returns.

Portfolio Turnover Risk.  The possibility that an underlying fund may frequently buy and sell portfolio securities, which may increase transaction costs to the underlying fund and cause the underlying fund’s performance to be less than you expect.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing an underlying fund to invest in fixed income securities with lower interest rates, which may adversely affect the underlying fund’s performance.

Redemption Risk.  The possibility that large redemptions may cause an underlying fund to sell its securities at inopportune times resulting in a loss to the underlying fund.

Sampling Risk.  The possibility that an underlying fund may not hold all of the securities included in its benchmark index and that the securities selected for the Fund, in the aggregate, will not provide investment performance matching that of the underlying fund’s benchmark index.

Tracking Error Risk.  The possibility that the underlying fund’s sub-adviser may not be able to cause the underlying fund’s performance to correspond to that of the underlying index, either on a daily or aggregate basis. Factors such as underlying fund expenses, imperfect correlation between the underlying fund’s investments and those of the underlying index, rounding of share prices, changes to the composition of the underlying index, regulatory policies, and high portfolio turnover rate all contribute to tracking error. Tracking error may cause the underlying fund’s performance to be less than you expect.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by an underlying fund if it is not obligated to do because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause an underlying fund’s share price or yield to fall.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in a fund which allocates its assets among various asset classes and market segments in the hope of achieving long-term growth and current income.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index and one additional index, the Bloomberg Barclays Capital U.S. Aggregate Bond Index. The Bloomberg Barclays Capital U.S. Aggregate Bond Index, in conjunction with the broad-based index, is used to track the broad range of allocations the Fund makes to the underlying funds. The foregoing indices, when considered together, may provide investors with a useful comparison of the Fund’s overall performance. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
10.51%	-6.23%
9/30/2009	3/31/2009

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Balanced Fund	1 Year	5 Years	Since Inception	Inception Date
Balanced Fund	14.32%	9.81%	8.23%	Aug. 25, 2008
S&P 500® Index (reflects no deduction for fees, expenses or taxes)	21.83%	15.79%	10.45%	Aug. 25, 2008
Bloomberg Barclays Capital U.S. Aggregate Bond Index (reflects no deduction for fees, expenses or taxes)	3.54%	2.10%	4.13%	Aug. 25, 2008

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Balanced Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  BALANCED FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Balanced Fund (the “Fund”) is to seek long-term growth and current income.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 9% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

9.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund seeks to achieve its investment objective by using a “fund-of-funds” strategy. Accordingly, the Fund invests in a combination of other Penn Series Funds (each, an “underlying fund” and, collectively, the “underlying funds”) in accordance with its target asset allocation. These underlying funds invest their assets directly in equity, fixed income, money market and other securities in accordance with their own investment objectives and policies. The underlying funds are managed using both indexed and active management strategies. The Fund intends to invest primarily in a combination of underlying funds; however, the Fund may invest directly in equity and fixed income securities and cash equivalents, including money market securities.

Under normal circumstances, the Fund will invest 50%-70% of its assets in stock and other equity underlying funds, 30%-50% of its assets in bond and other fixed income funds, and 0%-20% of its assets in money market funds. The Fund’s allocation strategy is designed to provide a mix of the growth opportunities of stock investing with the income opportunities of bonds and other fixed income securities.

The Fund’s underlying equity fund allocation will primarily track the performance of the large capitalization company portion of the U.S. stock market. The Fund’s underlying fixed income fund allocation will be invested primarily in a broad range of investment grade fixed income securities (although up to 10% of the underlying fund may be invested in non-investment grade securities (commonly known as “junk bonds”)), and is intended to provide results consistent with the broad U.S. fixed income market.

The following chart shows the Fund’s target asset allocation among the various asset classes. The Adviser may permit modest deviations from the target asset allocations listed below. Market appreciation or depreciation may cause the Fund to be outside of its target asset allocation range. In addition, differences in the performance of the underlying funds and the size and frequency of purchase and redemption orders may affect the Fund’s actual allocations. Accordingly, the Fund’s actual allocations may differ from this illustration.

Asset Classes and Underlying Funds	Target Asset Allocation
Equity Fund	50% - 70%
Penn Series Index 500 Fund
Fixed Income Fund	30% - 50%
Penn Series Quality Bond Fund
Money Market Fund	0% - 20%
Penn Series Money Market Fund

The Fund’s investment performance is directly related to the investment performance of the underlying funds. A brief description of each underlying fund’s principal investment strategy is provided below.

Underlying Funds	Investment Objective and Principal Investment Strategy
Penn Series Index 500 Fund	Seeks a total return (capital appreciation and income) which corresponds to that of the S&P 500® Index. Under normal circumstances, the Fund intends to invest substantially all of its assets in securities of companies included in the Index and close substitutes (such as index futures contracts) that are designed to track the S&P 500® Index.
Penn Series Quality Bond Fund	Seeks to maximize total return over the long term consistent with the preservation of capital. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in marketable investment grade debt securities.
Penn Series Money Market Fund	Seeks current income, while preserving capital and liquidity. The Fund is a government money market and will invest no less than 99.5% of its total assets in government securities, cash or repurchase agreements that are collateralized fully by government securities or cash.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Asset Allocation Risk.  The possibility that the Fund may underperform other funds with similar investment objectives due to the Fund’s allocation of assets to underlying funds investing in asset classes or market sectors that perform poorly relative to other asset categories.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Underlying Fund Investment Risk.  The possibility that the underperformance of an underlying fund may contribute to the underperformance of the Fund. The Fund’s performance and risks will be directly related to the performance and risks of the underlying funds in which it invests. In addition, the Fund indirectly pays a pro rata portion of the expenses incurred by the underlying funds, which also may lower the Fund’s performance.

Concentration Risk.  The possibility that, to the extent an underlying fund invests to a significant extent in a particular industry or group of industries within a particular sector, the underlying fund may be subject to greater risks than if its investments were broadly diversified across industries and sectors. The underlying fund also is subject to loss due to adverse occurrences that may affect that industry or group of industries.

Convertible Securities Risk.  The possibility that the value of an underlying fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by an underlying fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by an underlying fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Counterparty Risk.  The possibility that a party to a transaction involving an underlying fund may fail to meet its obligations thereby causing the underlying fund to lose money or the benefit of the transaction or preventing the underlying fund from selling or buying other securities to implement its investment strategies.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by an underlying fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of an underlying fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that an underlying fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Adviser or Sub-Adviser of the underlying fund believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Fixed Income Market Risk.  The possibility that the market value of a fixed-income security may decline due to general market conditions that are not specifically related to a particular company, such as real or perceived adverse economic conditions, changes in the outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. Fixed income securities markets may, in response to governmental intervention, economic or market developments (including potentially a reduction in the number of broker-dealers willing to engage in market-making activity), or other factors, experience periods of increased, and sometimes unpredictable, volatility and reduced liquidity. During those periods, an underlying fund may experience increased levels of shareholder redemptions, and may have to sell securities at inopportune times, and at unfavorable prices. Fixed income securities also may be difficult to value during such periods. In recent periods, governmental financial regulators, including the U.S. Federal Reserve, have taken steps to maintain historically low interest rates by purchasing bonds. Steps by those regulators to curtail or “taper” such activities could result in the effects described above, and could have a material adverse effect on prices for fixed income securities and on the management of an underlying fund.

Foreign Investment Risk.  The possibility that an underlying fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

High Yield Bond Risk.  The possibility that an underlying fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the underlying fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to an underlying fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Income Risk.  The possibility that an underlying fund’s yield (the rate of dividends the underlying fund pays) may decline in the event of declining interest rates.

Inflation Linked Bond Risk.  The possibility that the value of an underlying fund’s investments in inflation linked bonds will decline in value in response to a rise in real interest rates resulting in losses to the underlying fund. Inflation linked bonds may experience greater losses than other debt securities with similar durations when real interest rates rise faster than nominal interest rates.

Interest Rate Risk.  The possibility that the prices of an underlying fund’s fixed income investments will decline due to rising interest rates.

Investment Risk.  You may lose money by investing in the Money Market Fund. Although the Money Market Fund seeks to preserve the value of your investment at $1.00 per share, there is no guarantee that the Money Market Fund will be able to do so. An investment in the Money Market Fund is not insured or guaranteed by the FDIC or any other government agency. PMAM, the Fund’s sponsor, and its affiliates have no legal obligation to provide financial support to the Money Market Fund, and you should not expect that PMAM or its affiliates will provide financial support to the Money Market Fund at any time.

Large-Cap Securities Risk.  The possibility that an underlying fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of an underlying fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If an underlying fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Mortgage- and Asset-Backed Securities Risk.  The possibility that an underlying fund’s investments in mortgage- and asset-backed securities may decline in value and become less liquid when defaults on the underlying mortgages or assets occur and may exhibit additional volatility in periods of rising interest rates. Rising interest rates tend to extend the duration of these securities, making them more sensitive to changes in interest rates than instruments with fixed payment schedules. When interest rates decline or are low, the prepayment of mortgages or assets underlying such securities may reduce the underlying fund’s returns.

Portfolio Turnover Risk.  The possibility that an underlying fund may frequently buy and sell portfolio securities, which may increase transaction costs to the underlying fund and cause the underlying fund’s performance to be less than you expect.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing an underlying fund to invest in fixed income securities with lower interest rates, which may adversely affect the underlying fund’s performance.

Redemption Risk.  The possibility that large redemptions may cause an underlying fund to sell its securities at inopportune times resulting in a loss to the underlying fund.

Sampling Risk.  The possibility that an underlying fund may not hold all of the securities included in its benchmark index and that the securities selected for the Fund, in the aggregate, will not provide investment performance matching that of the underlying fund’s benchmark index.

Tracking Error Risk.  The possibility that the underlying fund’s sub-adviser may not be able to cause the underlying fund’s performance to correspond to that of the underlying index, either on a daily or aggregate basis. Factors such as underlying fund expenses, imperfect correlation between the underlying fund’s investments and those of the underlying index, rounding of share prices, changes to the composition of the underlying index, regulatory policies, and high portfolio turnover rate all contribute to tracking error. Tracking error may cause the underlying fund’s performance to be less than you expect.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by an underlying fund if it is not obligated to do because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause an underlying fund’s share price or yield to fall.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in a fund which allocates its assets among various asset classes and market segments in the hope of achieving long-term growth and current income.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index and one additional index, the Bloomberg Barclays Capital U.S. Aggregate Bond Index. The Bloomberg Barclays Capital U.S. Aggregate Bond Index, in conjunction with the broad-based index, is used to track the broad range of allocations the Fund makes to the underlying funds. The foregoing indices, when considered together, may provide investors with a useful comparison of the Fund’s overall performance. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index and one additional index, the Bloomberg Barclays Capital U.S. Aggregate Bond Index.

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

The Bloomberg Barclays Capital U.S. Aggregate Bond Index, in conjunction with the broad-based index, is used to track the broad range of allocations the Fund makes to the underlying funds. The foregoing indices, when considered together, may provide investors with a useful comparison of the Fund’s overall performance.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
10.51%	-6.23%
9/30/2009	3/31/2009

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Balanced Fund | Balanced Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

none

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.19%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.48%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.67%

^[1]

1 Year

rr_ExpenseExampleYear01

$ 68

3 Years

rr_ExpenseExampleYear03

214

5 Years

rr_ExpenseExampleYear05

373

10 Years

rr_ExpenseExampleYear10

$ 835

2009

rr_AnnualReturn2009

18.07%

2010

rr_AnnualReturn2010

11.69%

2011

rr_AnnualReturn2011

5.56%

2012

rr_AnnualReturn2012

10.53%

2013

rr_AnnualReturn2013

16.75%

2014

rr_AnnualReturn2014

9.65%

2015

rr_AnnualReturn2015

0.68%

2016

rr_AnnualReturn2016

8.37%

2017

rr_AnnualReturn2017

14.32%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

10.51%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Mar. 31, 2009

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(6.23%)

1 Year

rr_AverageAnnualReturnYear01

14.32%

5 Years

rr_AverageAnnualReturnYear05

9.81%

Since Inception

rr_AverageAnnualReturnSinceInception

8.23%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Balanced Fund | S&P 500® Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

21.83%

5 Years

rr_AverageAnnualReturnYear05

15.79%

Since Inception

rr_AverageAnnualReturnSinceInception

10.45%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Balanced Fund | Bloomberg Barclays Capital U.S. Aggregate Bond Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

3.54%

5 Years

rr_AverageAnnualReturnYear05

2.10%

Since Inception

rr_AverageAnnualReturnSinceInception

4.13%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Penn Series Large Growth Stock Fund

FUND SUMMARY:  LARGE GROWTH STOCK FUND

Investment Objective

The investment objective of the Large Growth Stock Fund (the “Fund”) is to achieve long-term growth of capital and increase of future income.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Large Growth Stock Fund Large Growth Stock Fund
Investment Advisory Fees	0.71%
Distribution (12b-1) Fees	none
Other Expenses	0.25%
Total Annual Fund Operating Expenses	0.96%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Large Growth Stock Fund | Large Growth Stock Fund | USD ($)	98	306	531	1,178

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 52% of the average value of its portfolio.

Principal Investment Strategy

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in common stocks of large capitalization companies. For purposes of this policy, large capitalization companies have market capitalizations that fall within the market capitalization range of companies in the Russell 1000^® Growth Index at the time of purchase (as of March 31, 2018, this range was between $1.3 billion and $851.3 billion). Because the Fund’s definition of large capitalization companies is dynamic, the lower and upper limits on market capitalization will change with the markets. The Fund will invest primarily in common stocks of well established companies the Sub-Adviser believes have long-term growth potential. In selecting the Fund’s investments, the Sub-Adviser seeks investments in companies that have the ability to pay increasing dividends through strong cash flow. The Sub-Adviser’s approach looks for companies with an above-average rate of earnings growth and a lucrative niche in the economy that gives them the ability to sustain earnings momentum even during times of slow economic growth. The Sub-Adviser believes when a company increases its earnings faster than both inflation and the overall economy, the market will eventually reward it with a higher stock price. The Fund may at times invest significantly in technology stocks. The Fund may sell securities for a variety of reasons, such as to secure gains, limit losses, or redeploy assets into more promising opportunities.

In pursuing its investment objective, the Sub-Adviser has the discretion to purchase some securities that do not meet its normal investment criteria, as described above, when it perceives an unusual opportunity for gain. Those situations might arise when the Sub-Adviser believes a security could increase in value for a variety of reasons, including a change in management, an extraordinary corporate event, a new product introduction or innovation, or a favorable competitive development.

While most assets will be invested in exchange-listed U.S. common stocks, other securities may also be purchased, including foreign stocks (up to 30% of total assets), convertible securities, and preferred stocks, in keeping with the Fund’s objectives.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that the Fund’s investments in securities of companies perceived to be “growth” companies may underperform when the Fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

Information Technology Industry Risk.  To the extent the Fund invests in specific industries or sectors, it may be more susceptible to developments affecting those industries and sectors. For example, the Fund may at times have significant investments in technology companies, which could result in the Fund performing poorly during a downturn in one or more of the industries that heavily impact technology companies. Technology companies can be adversely affected by, among other things, intense competition, earnings disappointments, and rapid obsolescence of products and services due to technological innovations or changing consumer preferences.

Large-Cap Securities Risk.  The possibility that the Fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in common stocks in the hope of earning above-average long-term growth of capital and income.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
19.01%	-23.79%
3/31/2012	12/31/2008

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Large Growth Stock Fund	1 Year	5 Years	10 Years
Large Growth Stock Fund	33.16%	17.53%	9.79%
Russell 1000® Growth Index (reflects no deduction for fees, expenses or taxes)	30.21%	17.33%	10.00%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Large Growth Stock Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  LARGE GROWTH STOCK FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Large Growth Stock Fund (the “Fund”) is to achieve long-term growth of capital and increase of future income.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 52% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

52.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in common stocks of large capitalization companies. For purposes of this policy, large capitalization companies have market capitalizations that fall within the market capitalization range of companies in the Russell 1000^® Growth Index at the time of purchase (as of March 31, 2018, this range was between $1.3 billion and $851.3 billion). Because the Fund’s definition of large capitalization companies is dynamic, the lower and upper limits on market capitalization will change with the markets. The Fund will invest primarily in common stocks of well established companies the Sub-Adviser believes have long-term growth potential. In selecting the Fund’s investments, the Sub-Adviser seeks investments in companies that have the ability to pay increasing dividends through strong cash flow. The Sub-Adviser’s approach looks for companies with an above-average rate of earnings growth and a lucrative niche in the economy that gives them the ability to sustain earnings momentum even during times of slow economic growth. The Sub-Adviser believes when a company increases its earnings faster than both inflation and the overall economy, the market will eventually reward it with a higher stock price. The Fund may at times invest significantly in technology stocks. The Fund may sell securities for a variety of reasons, such as to secure gains, limit losses, or redeploy assets into more promising opportunities.

In pursuing its investment objective, the Sub-Adviser has the discretion to purchase some securities that do not meet its normal investment criteria, as described above, when it perceives an unusual opportunity for gain. Those situations might arise when the Sub-Adviser believes a security could increase in value for a variety of reasons, including a change in management, an extraordinary corporate event, a new product introduction or innovation, or a favorable competitive development.

While most assets will be invested in exchange-listed U.S. common stocks, other securities may also be purchased, including foreign stocks (up to 30% of total assets), convertible securities, and preferred stocks, in keeping with the Fund’s objectives.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that the Fund’s investments in securities of companies perceived to be “growth” companies may underperform when the Fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

Information Technology Industry Risk.  To the extent the Fund invests in specific industries or sectors, it may be more susceptible to developments affecting those industries and sectors. For example, the Fund may at times have significant investments in technology companies, which could result in the Fund performing poorly during a downturn in one or more of the industries that heavily impact technology companies. Technology companies can be adversely affected by, among other things, intense competition, earnings disappointments, and rapid obsolescence of products and services due to technological innovations or changing consumer preferences.

Large-Cap Securities Risk.  The possibility that the Fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in common stocks in the hope of earning above-average long-term growth of capital and income.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
19.01%	-23.79%
3/31/2012	12/31/2008

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Large Growth Stock Fund | Large Growth Stock Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.71%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.25%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.96%

1 Year

rr_ExpenseExampleYear01

$ 98

3 Years

rr_ExpenseExampleYear03

306

5 Years

rr_ExpenseExampleYear05

531

10 Years

rr_ExpenseExampleYear10

$ 1,178

2008

rr_AnnualReturn2008

(41.87%)

2009

rr_AnnualReturn2009

42.93%

2010

rr_AnnualReturn2010

16.79%

2011

rr_AnnualReturn2011

(1.55%)

2012

rr_AnnualReturn2012

18.75%

2013

rr_AnnualReturn2013

39.11%

2014

rr_AnnualReturn2014

8.36%

2015

rr_AnnualReturn2015

10.51%

2016

rr_AnnualReturn2016

1.10%

2017

rr_AnnualReturn2017

33.16%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2012

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

19.01%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(23.79%)

1 Year

rr_AverageAnnualReturnYear01

33.16%

5 Years

rr_AverageAnnualReturnYear05

17.53%

10 Years

rr_AverageAnnualReturnYear10

9.79%

Penn Series Large Growth Stock Fund | Russell 1000® Growth Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

30.21%

5 Years

rr_AverageAnnualReturnYear05

17.33%

10 Years

rr_AverageAnnualReturnYear10

10.00%

XML

Penn Series Large Cap Growth Fund

FUND SUMMARY:  LARGE CAP GROWTH FUND

Investment Objective

The investment objective of the Large Cap Growth Fund (the “Fund”) is to seek long-term capital appreciation.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Large Cap Growth Fund Large Cap Growth Fund
Investment Advisory Fees	0.55%
Distribution (12b-1) Fees	none
Other Expenses	0.34%
Total Annual Fund Operating Expenses	0.89%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Large Cap Growth Fund | Large Cap Growth Fund | USD ($)	91	284	493	1,096

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 28% of the average value of its portfolio.

Principal Investment Strategy

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in common stocks of U.S. companies with large market capitalizations. For purposes of this policy, large capitalization companies have market capitalizations of more than $3 billion at the time of purchase. The Sub-Adviser focuses on investing the Fund’s assets in the stocks of companies it believes to have above average earnings growth potential compared to other companies (i.e., growth companies). Growth companies tend to have stock prices that are high relative to their earnings, dividends, book value, or other financial measures. While the Fund primarily invests in the common stocks of large capitalization companies, the Fund may invest a portion of its net assets (no more than 20%) in small and medium capitalization companies with market capitalizations of less than $3 billion at the time of purchase. The Sub-Adviser normally invests the Fund’s assets across different industries and sectors, but the Sub-Adviser may invest a significant percentage of the Fund’s assets in a single industry or sector. The Fund also may invest up to 20% of its net assets in foreign securities at the time of purchase. The Fund may participate in initial public offerings (“IPOs”).

The Sub-Adviser uses an active bottom-up investment approach to buying and selling investments for the Fund. Investments are selected primarily based on fundamental analysis of individual issuers and their potential in light of their financial condition, and market, economic, political, and regulatory conditions. Factors considered may include analysis of an issuer’s earnings, cash flows, competitive position, and management ability. Quantitative models that systematically evaluate an issuer’s valuation, price and earnings momentum, earnings quality, and other factors may also be considered.

Due to its investment strategy, the Fund may buy and sell securities frequently, which may result in higher transaction costs and may lower fund performance.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Focus Risk.  Issuers in a single industry, sector, country, or region can react similarly to market, currency, political, economic, regulatory, geopolitical, and other conditions, and the Fund’s performance will be affected by the conditions in the industries, sectors, countries and regions to which the Fund is exposed.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that the Fund’s investments in securities of companies perceived to be “growth” companies may underperform when the Fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

IPOs Risk.  The possibility that the Fund’s performance may be affected by the purchase of securities issued in initial public offerings (IPOs) that have little to no trading history, limited issuer information, increased volatility and may not be available to the extent desired. The prices of securities bought in IPOs may rise and fall rapidly, often because of investor perceptions rather than economic reasons.

Large-Cap Securities Risk.  The possibility that the Fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Portfolio Turnover Risk.  The possibility that the Fund may frequently buy and sell portfolio securities, which may increase transaction costs to the Fund and cause the Fund’s performance to be less than you expect.

Small- and Mid-Cap Securities Risk.  The possibility that the Fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and the Fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in common stocks in the hope of long-term capital appreciation.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Performance prior to May 1, 2013 reflects the Fund’s investment performance when managed by a previous sub-adviser pursuant to a substantially similar principal investment strategy. Since May 1, 2013, Massachusetts Financial Services Company has been responsible for the Fund’s day-to-day portfolio management. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
17.05%	-26.16%
3/31/2012	12/31/2008

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Large Cap Growth Fund	1 Year	5 Years	10 Years
Large Cap Growth Fund	28.19%	13.19%	5.19%
Russell 1000® Growth Index (reflects no deduction for fees, expenses or taxes)	30.21%	17.33%	10.00%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Large Cap Growth Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  LARGE CAP GROWTH FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Large Cap Growth Fund (the “Fund”) is to seek long-term capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 28% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

28.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in common stocks of U.S. companies with large market capitalizations. For purposes of this policy, large capitalization companies have market capitalizations of more than $3 billion at the time of purchase. The Sub-Adviser focuses on investing the Fund’s assets in the stocks of companies it believes to have above average earnings growth potential compared to other companies (i.e., growth companies). Growth companies tend to have stock prices that are high relative to their earnings, dividends, book value, or other financial measures. While the Fund primarily invests in the common stocks of large capitalization companies, the Fund may invest a portion of its net assets (no more than 20%) in small and medium capitalization companies with market capitalizations of less than $3 billion at the time of purchase. The Sub-Adviser normally invests the Fund’s assets across different industries and sectors, but the Sub-Adviser may invest a significant percentage of the Fund’s assets in a single industry or sector. The Fund also may invest up to 20% of its net assets in foreign securities at the time of purchase. The Fund may participate in initial public offerings (“IPOs”).

The Sub-Adviser uses an active bottom-up investment approach to buying and selling investments for the Fund. Investments are selected primarily based on fundamental analysis of individual issuers and their potential in light of their financial condition, and market, economic, political, and regulatory conditions. Factors considered may include analysis of an issuer’s earnings, cash flows, competitive position, and management ability. Quantitative models that systematically evaluate an issuer’s valuation, price and earnings momentum, earnings quality, and other factors may also be considered.

Due to its investment strategy, the Fund may buy and sell securities frequently, which may result in higher transaction costs and may lower fund performance.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Focus Risk.  Issuers in a single industry, sector, country, or region can react similarly to market, currency, political, economic, regulatory, geopolitical, and other conditions, and the Fund’s performance will be affected by the conditions in the industries, sectors, countries and regions to which the Fund is exposed.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that the Fund’s investments in securities of companies perceived to be “growth” companies may underperform when the Fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

IPOs Risk.  The possibility that the Fund’s performance may be affected by the purchase of securities issued in initial public offerings (IPOs) that have little to no trading history, limited issuer information, increased volatility and may not be available to the extent desired. The prices of securities bought in IPOs may rise and fall rapidly, often because of investor perceptions rather than economic reasons.

Large-Cap Securities Risk.  The possibility that the Fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Portfolio Turnover Risk.  The possibility that the Fund may frequently buy and sell portfolio securities, which may increase transaction costs to the Fund and cause the Fund’s performance to be less than you expect.

Small- and Mid-Cap Securities Risk.  The possibility that the Fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and the Fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in common stocks in the hope of long-term capital appreciation.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

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Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Performance prior to May 1, 2013 reflects the Fund’s investment performance when managed by a previous sub-adviser pursuant to a substantially similar principal investment strategy. Since May 1, 2013, Massachusetts Financial Services Company has been responsible for the Fund’s day-to-day portfolio management. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
17.05%	-26.16%
3/31/2012	12/31/2008

Performance Table Heading

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Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Large Cap Growth Fund | Large Cap Growth Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.55%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.34%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.89%

1 Year

rr_ExpenseExampleYear01

$ 91

3 Years

rr_ExpenseExampleYear03

284

5 Years

rr_ExpenseExampleYear05

493

10 Years

rr_ExpenseExampleYear10

$ 1,096

2008

rr_AnnualReturn2008

(43.82%)

2009

rr_AnnualReturn2009

37.54%

2010

rr_AnnualReturn2010

12.44%

2011

rr_AnnualReturn2011

(6.77%)

2012

rr_AnnualReturn2012

10.25%

2013

rr_AnnualReturn2013

23.09%

2014

rr_AnnualReturn2014

11.29%

2015

rr_AnnualReturn2015

(0.15%)

2016

rr_AnnualReturn2016

5.96%

2017

rr_AnnualReturn2017

28.19%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2012

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

17.05%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(26.16%)

1 Year

rr_AverageAnnualReturnYear01

28.19%

5 Years

rr_AverageAnnualReturnYear05

13.19%

10 Years

rr_AverageAnnualReturnYear10

5.19%

Penn Series Large Cap Growth Fund | Russell 1000® Growth Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

30.21%

5 Years

rr_AverageAnnualReturnYear05

17.33%

10 Years

rr_AverageAnnualReturnYear10

10.00%

XML

Penn Series Large Core Growth Fund

FUND SUMMARY:  LARGE CORE GROWTH FUND

Investment Objective

The investment objective of the Large Core Growth Fund (the “Fund”) is to seek to achieve long-term growth of capital (capital appreciation).

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Large Core Growth Fund Large Core Growth Fund
Investment Advisory Fees	0.60%
Distribution (12b-1) Fees	none
Other Expenses	0.26%
Total Annual Fund Operating Expenses	0.86%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Large Core Growth Fund | Large Core Growth Fund | USD ($)	88	274	477	1,061

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 64% of the average value of its portfolio.

Principal Investment Strategy

The Fund attempts to achieve its investment objective by investing primarily in equity securities of large capitalization U.S. companies. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities of large capitalization companies. For purposes of this policy, large capitalization companies have market capitalizations that fall within the market capitalization range of companies in the Russell 1000^® Growth Index at the time of purchase (as of March 31, 2018, this range was between $344.3 million and $850.7 billion). Because the Fund’s definition of large capitalization companies is dynamic, the lower and upper limits on market capitalization will change with the markets.

The Sub-Adviser emphasizes a bottom-up stock selection process, seeking attractive investments on an individual company basis. In selecting securities for investment, the Sub-Adviser seeks to invest in companies with strong name recognition, as determined by a company’s brand, market leadership or dominance, and network effects, and sustainable competitive advantages that permit growth and scale over time. The Sub-Adviser typically favors companies with rising returns on invested capital, above average business visibility, strong free cash flow generation and an attractive risk/reward.

Fundamental research drives the investment process. The Sub-Adviser studies on an ongoing basis company developments, including business strategy and financial results. The Sub-Adviser generally considers selling a portfolio holding when it determines that the holding no longer satisfies its investment criteria.

The Fund may invest in foreign securities, which may include emerging market securities.

The Fund’s equity investments may include common and preferred stocks, convertible securities and equity-linked securities, rights and warrants to purchase common stocks, depositary receipts, exchange-traded funds (“ETFs”) and limited partnership interests. The Fund may invest in privately placed and restricted securities.

Derivative instruments used by the Fund will be counted toward the Fund’s 80% policy discussed above to the extent they have economic characteristics similar to the securities included within that policy.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Convertible Securities Risk.  The possibility that the value of the Fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Depositary Receipt Risk.  The possibility that the Fund’s investments in foreign companies through depositary receipts will expose the Fund to the same risks as direct investment in securities of foreign issuers. In addition, investments in ADRs may be less liquid than the underlying shares in their primary trading market, and the value of securities underlying ADRs may change materially at times when U.S. markets are not open for trading.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity-Linked Securities Risk.  Equity-linked securities, which are privately issued securities whose investment results are designed to correspond generally to the performance of a specified stock index or “basket” of stocks, or a single stock, are subject to equity securities risk. In addition, to the extent that the Fund invests in equity-linked securities whose return corresponds to the performance of a foreign security index or one or more foreign stocks, investing in equity-linked securities will involve risks similar to the risks of investing in foreign securities and will be subject to the Fund’s restrictions on investments in foreign securities. Equity-linked securities may also be subject to both counterparty credit and liquidity risk.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that the Fund’s investments in securities of companies perceived to be “growth” companies may underperform when the Fund’s investment strategy shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

Large-Cap Securities Risk.  The possibility that the Fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Other Investment Company Risk.  The possibility that investments by the Fund in shares of other investment companies will subject the Fund to the risks associated with those investment companies. Fund shareholders will also indirectly bear a proportionate share of any underlying investment company’s fees and expenses in addition to paying the Fund’s expenses.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in equity securities in the hope of achieving long-term growth of capital.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Performance prior to December 1, 2016 reflects the Fund’s investment performance when managed by a previous sub-adviser pursuant to a substantially similar principal investment strategy. Since December 1, 2016, Morgan Stanley Investment Management Inc. has been responsible for the Fund’s day-to-day portfolio management. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
18.51%	-17.53%
3/31/2012	9/30/2011

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Large Core Growth Fund	1 Year	5 Years	Since Inception	Inception Date
Large Core Growth Fund	32.78%	14.97%	8.66%	Aug. 25, 2008
Russell 1000® Growth Index (reflects no deduction for fees, expenses or taxes)	30.21%	17.33%	11.79%	Aug. 25, 2008

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Large Core Growth Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  LARGE CORE GROWTH FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Large Core Growth Fund (the “Fund”) is to seek to achieve long-term growth of capital (capital appreciation).

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 64% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

64.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund attempts to achieve its investment objective by investing primarily in equity securities of large capitalization U.S. companies. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities of large capitalization companies. For purposes of this policy, large capitalization companies have market capitalizations that fall within the market capitalization range of companies in the Russell 1000^® Growth Index at the time of purchase (as of March 31, 2018, this range was between $344.3 million and $850.7 billion). Because the Fund’s definition of large capitalization companies is dynamic, the lower and upper limits on market capitalization will change with the markets.

The Sub-Adviser emphasizes a bottom-up stock selection process, seeking attractive investments on an individual company basis. In selecting securities for investment, the Sub-Adviser seeks to invest in companies with strong name recognition, as determined by a company’s brand, market leadership or dominance, and network effects, and sustainable competitive advantages that permit growth and scale over time. The Sub-Adviser typically favors companies with rising returns on invested capital, above average business visibility, strong free cash flow generation and an attractive risk/reward.

Fundamental research drives the investment process. The Sub-Adviser studies on an ongoing basis company developments, including business strategy and financial results. The Sub-Adviser generally considers selling a portfolio holding when it determines that the holding no longer satisfies its investment criteria.

The Fund may invest in foreign securities, which may include emerging market securities.

The Fund’s equity investments may include common and preferred stocks, convertible securities and equity-linked securities, rights and warrants to purchase common stocks, depositary receipts, exchange-traded funds (“ETFs”) and limited partnership interests. The Fund may invest in privately placed and restricted securities.

Derivative instruments used by the Fund will be counted toward the Fund’s 80% policy discussed above to the extent they have economic characteristics similar to the securities included within that policy.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Convertible Securities Risk.  The possibility that the value of the Fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Depositary Receipt Risk.  The possibility that the Fund’s investments in foreign companies through depositary receipts will expose the Fund to the same risks as direct investment in securities of foreign issuers. In addition, investments in ADRs may be less liquid than the underlying shares in their primary trading market, and the value of securities underlying ADRs may change materially at times when U.S. markets are not open for trading.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity-Linked Securities Risk.  Equity-linked securities, which are privately issued securities whose investment results are designed to correspond generally to the performance of a specified stock index or “basket” of stocks, or a single stock, are subject to equity securities risk. In addition, to the extent that the Fund invests in equity-linked securities whose return corresponds to the performance of a foreign security index or one or more foreign stocks, investing in equity-linked securities will involve risks similar to the risks of investing in foreign securities and will be subject to the Fund’s restrictions on investments in foreign securities. Equity-linked securities may also be subject to both counterparty credit and liquidity risk.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that the Fund’s investments in securities of companies perceived to be “growth” companies may underperform when the Fund’s investment strategy shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

Large-Cap Securities Risk.  The possibility that the Fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Other Investment Company Risk.  The possibility that investments by the Fund in shares of other investment companies will subject the Fund to the risks associated with those investment companies. Fund shareholders will also indirectly bear a proportionate share of any underlying investment company’s fees and expenses in addition to paying the Fund’s expenses.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in equity securities in the hope of achieving long-term growth of capital.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Performance prior to December 1, 2016 reflects the Fund’s investment performance when managed by a previous sub-adviser pursuant to a substantially similar principal investment strategy. Since December 1, 2016, Morgan Stanley Investment Management Inc. has been responsible for the Fund’s day-to-day portfolio management. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
18.51%	-17.53%
3/31/2012	9/30/2011

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Large Core Growth Fund | Large Core Growth Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.60%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.26%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.86%

1 Year

rr_ExpenseExampleYear01

$ 88

3 Years

rr_ExpenseExampleYear03

274

5 Years

rr_ExpenseExampleYear05

477

10 Years

rr_ExpenseExampleYear10

$ 1,061

2009

rr_AnnualReturn2009

35.89%

2010

rr_AnnualReturn2010

17.27%

2011

rr_AnnualReturn2011

(5.01%)

2012

rr_AnnualReturn2012

16.15%

2013

rr_AnnualReturn2013

37.91%

2014

rr_AnnualReturn2014

7.73%

2015

rr_AnnualReturn2015

1.68%

2016

rr_AnnualReturn2016

0.12%

2017

rr_AnnualReturn2017

32.78%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2012

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

18.51%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(17.53%)

1 Year

rr_AverageAnnualReturnYear01

32.78%

5 Years

rr_AverageAnnualReturnYear05

14.97%

Since Inception

rr_AverageAnnualReturnSinceInception

8.66%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Large Core Growth Fund | Russell 1000® Growth Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

30.21%

5 Years

rr_AverageAnnualReturnYear05

17.33%

Since Inception

rr_AverageAnnualReturnSinceInception

11.79%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

XML

Penn Series Large Cap Value Fund

FUND SUMMARY:  LARGE CAP VALUE FUND

Investment Objective

The investment objective of the Large Cap Value Fund (the “Fund”) is to seek to achieve long-term growth of capital.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Large Cap Value Fund Large Cap Value Fund
Investment Advisory Fees	0.66%
Distribution (12b-1) Fees	none
Other Expenses	0.24%
Total Annual Fund Operating Expenses	0.90%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Large Cap Value Fund | Large Cap Value Fund | USD ($)	92	287	498	1,108

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 17% of the average value of its portfolio.

Principal Investment Strategy

The Fund will invest primarily in equity securities, of U.S. and non-U.S. incorporated entities, including, but not limited to common stock, American Depositary Receipts (“ADRs”), equity real estate investment trusts (“REITs”), preferred securities and convertible preferred securities. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of large capitalization companies. For purposes of this policy, large capitalization companies are those with market-capitalizations greater than $2 billion. The Fund primarily invests in common stocks that the Sub-Adviser deems to be underpriced relative to long-term earnings and for cash flow potential.

The Sub-Adviser attempts to reduce the Fund’s exposure to market risks by diversifying its investments, that is, by not holding a substantial amount of stock of any one company and by not investing too great a percentage of the Fund’s assets in any one company. In selecting securities for purchase or sale by the Fund, the Sub-Adviser selects securities one at a time before considering industry trends. This is called a “bottom-up approach.” The Sub-Adviser uses a fundamental analysis to select securities that it believes are undervalued relative to long-term earnings and cash flow potential. While this process and the inter-relationship of the factors used may change over time and its implementation may vary in particular cases, the Sub-Adviser currently considers one or more of the following factors when assessing a company’s business prospects: attractive valuation, future supply/demand conditions for its key products, product cycles, quality of management, competitive position in the market place, reinvestment plans for cash generated, and better-than-expected earnings reports. The Sub-Adviser may consider selling a stock for one or more of the following reasons: the stock price is approaching its target, the company’s fundamentals are deteriorating, or alternative investment ideas have been developed.

While the Fund primarily invests in large capitalization companies, the Fund may invest a portion of its assets (no more than 20%) in small and medium capitalization companies. In addition to common stocks, the Fund may invest in other equity securities, including preferred stocks, warrants, rights, and convertible securities. The Fund may also invest up to 25% of its assets in securities of foreign issuers, options for hedging and investment purposes, and REITs. The Fund anticipates investing primarily in equity REITs as opposed to mortgage or other types of REITs, which generally invest in and own properties, such as commercial properties, and generate revenue from these property rents. The Fund may also invest up to 15% of its assets in securities issued pursuant to Rule 144A under the Securities Act of 1933 (“Rule 144A Securities”).

Except as provided above and subject to the provisions of the 1940 Act, the Fund is not limited in the percentage of its assets that it may invest in these instruments. Securities of foreign issuers that are represented by ADRs or that are listed on a U.S. securities exchange or traded in the U.S. over-the-counter markets are not considered “foreign securities” for purposes of this investment restriction. The Fund may invest up to 5% of its assets, as determined at the time of purchase, in any one company.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Convertible Securities Risk.  The possibility that the value of the Fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Depositary Receipt Risk.  The possibility that the Fund’s investments in foreign companies through depositary receipts will expose the Fund to the same risks as direct investment in securities of foreign issuers. In addition, investments in ADRs may be less liquid than the underlying shares in their primary trading market, and the value of securities underlying ADRs may change materially at times when U.S. markets are not open for trading.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

Interest Rate Risk.  The possibility that the prices of the Fund’s convertible securities will decline due to rising interest rates.

Large-Cap Securities Risk.  The possibility that the Fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Portfolio Turnover Risk.  The possibility that the Fund may frequently buy and sell portfolio securities, which may increase transaction costs to the Fund and cause the Fund’s performance to be less than you expect.

Preferred Stock Risk.  The possibility that the value of the Fund’s investments in preferred stock may decline if stock prices fall or interest rates rise. In the event of a liquidation, the rights of a company’s preferred stock to the distribution of company assets are generally subordinate to the rights of a company’s debt securities.

REITs Risk.  The possibility that the Fund’s investments in REITs will subject the Fund to the risks associated with the direct ownership of real estate, including fluctuations in the value of underlying properties, changes in interest rates and risks related to general or local economic conditions. REITs are dependent upon management skills and generally may not be diversified. REITs are also subject to heavy cash flow dependency, defaults by borrowers or tenants and self-liquidation.

Rule 144A Securities Risk.  The possibility that the Fund’s investment in Rule 144A Securities will subject the Fund to liquidity risk if there are an insufficient number of qualified institutional buyers interested in purchasing Rule 144A Securities held by the Fund leading to the Fund’s inability to sell its Rule 144A Securities at a time desired by the Fund or at prices approximating the value at which the Fund is carrying the securities on its books.

Small- and Mid-Cap Securities Risk.  The possibility that the Fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and the Fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

“Value” Investing Risk.  The possibility that the Fund’s investments in securities believed by the Sub-Adviser to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which the Fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the Fund’s investment style shifts out of favor.

Warrants Risk.  The possibility that the Fund’s investments in warrants are subject to greater price volatility than the warrants’ underlying securities. Warrants offer greater potential for profit or loss than an equivalent investment in the underlying security. A warrant generally ceases to have value if it is not exercised prior to its expiration date.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing primarily in equity securities of large capitalization companies in the hope of earning long-term growth of capital.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Performance prior to May 1, 2013 reflects the Fund’s investment performance when managed by a previous sub-adviser pursuant to a substantially similar principal investment strategy. Since May 1, 2013, Loomis, Sayles & Company, L.P. has been responsible for the Fund’s day-to-day portfolio management. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
19.07%	-26.40%
6/30/2009	12/31/2008

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Large Cap Value Fund	1 Year	5 Years	10 Years
Large Cap Value Fund	14.60%	12.65%	5.25%
Russell 1000® Value Index (reflects no deduction for fees, expenses or taxes)	13.66%	14.04%	7.10%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Large Cap Value Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  LARGE CAP VALUE FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Large Cap Value Fund (the “Fund”) is to seek to achieve long-term growth of capital.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 17% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

17.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund will invest primarily in equity securities, of U.S. and non-U.S. incorporated entities, including, but not limited to common stock, American Depositary Receipts (“ADRs”), equity real estate investment trusts (“REITs”), preferred securities and convertible preferred securities. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of large capitalization companies. For purposes of this policy, large capitalization companies are those with market-capitalizations greater than $2 billion. The Fund primarily invests in common stocks that the Sub-Adviser deems to be underpriced relative to long-term earnings and for cash flow potential.

The Sub-Adviser attempts to reduce the Fund’s exposure to market risks by diversifying its investments, that is, by not holding a substantial amount of stock of any one company and by not investing too great a percentage of the Fund’s assets in any one company. In selecting securities for purchase or sale by the Fund, the Sub-Adviser selects securities one at a time before considering industry trends. This is called a “bottom-up approach.” The Sub-Adviser uses a fundamental analysis to select securities that it believes are undervalued relative to long-term earnings and cash flow potential. While this process and the inter-relationship of the factors used may change over time and its implementation may vary in particular cases, the Sub-Adviser currently considers one or more of the following factors when assessing a company’s business prospects: attractive valuation, future supply/demand conditions for its key products, product cycles, quality of management, competitive position in the market place, reinvestment plans for cash generated, and better-than-expected earnings reports. The Sub-Adviser may consider selling a stock for one or more of the following reasons: the stock price is approaching its target, the company’s fundamentals are deteriorating, or alternative investment ideas have been developed.

While the Fund primarily invests in large capitalization companies, the Fund may invest a portion of its assets (no more than 20%) in small and medium capitalization companies. In addition to common stocks, the Fund may invest in other equity securities, including preferred stocks, warrants, rights, and convertible securities. The Fund may also invest up to 25% of its assets in securities of foreign issuers, options for hedging and investment purposes, and REITs. The Fund anticipates investing primarily in equity REITs as opposed to mortgage or other types of REITs, which generally invest in and own properties, such as commercial properties, and generate revenue from these property rents. The Fund may also invest up to 15% of its assets in securities issued pursuant to Rule 144A under the Securities Act of 1933 (“Rule 144A Securities”).

Except as provided above and subject to the provisions of the 1940 Act, the Fund is not limited in the percentage of its assets that it may invest in these instruments. Securities of foreign issuers that are represented by ADRs or that are listed on a U.S. securities exchange or traded in the U.S. over-the-counter markets are not considered “foreign securities” for purposes of this investment restriction. The Fund may invest up to 5% of its assets, as determined at the time of purchase, in any one company.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Convertible Securities Risk.  The possibility that the value of the Fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Depositary Receipt Risk.  The possibility that the Fund’s investments in foreign companies through depositary receipts will expose the Fund to the same risks as direct investment in securities of foreign issuers. In addition, investments in ADRs may be less liquid than the underlying shares in their primary trading market, and the value of securities underlying ADRs may change materially at times when U.S. markets are not open for trading.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

Interest Rate Risk.  The possibility that the prices of the Fund’s convertible securities will decline due to rising interest rates.

Large-Cap Securities Risk.  The possibility that the Fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Portfolio Turnover Risk.  The possibility that the Fund may frequently buy and sell portfolio securities, which may increase transaction costs to the Fund and cause the Fund’s performance to be less than you expect.

Preferred Stock Risk.  The possibility that the value of the Fund’s investments in preferred stock may decline if stock prices fall or interest rates rise. In the event of a liquidation, the rights of a company’s preferred stock to the distribution of company assets are generally subordinate to the rights of a company’s debt securities.

REITs Risk.  The possibility that the Fund’s investments in REITs will subject the Fund to the risks associated with the direct ownership of real estate, including fluctuations in the value of underlying properties, changes in interest rates and risks related to general or local economic conditions. REITs are dependent upon management skills and generally may not be diversified. REITs are also subject to heavy cash flow dependency, defaults by borrowers or tenants and self-liquidation.

Rule 144A Securities Risk.  The possibility that the Fund’s investment in Rule 144A Securities will subject the Fund to liquidity risk if there are an insufficient number of qualified institutional buyers interested in purchasing Rule 144A Securities held by the Fund leading to the Fund’s inability to sell its Rule 144A Securities at a time desired by the Fund or at prices approximating the value at which the Fund is carrying the securities on its books.

Small- and Mid-Cap Securities Risk.  The possibility that the Fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and the Fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

“Value” Investing Risk.  The possibility that the Fund’s investments in securities believed by the Sub-Adviser to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which the Fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the Fund’s investment style shifts out of favor.

Warrants Risk.  The possibility that the Fund’s investments in warrants are subject to greater price volatility than the warrants’ underlying securities. Warrants offer greater potential for profit or loss than an equivalent investment in the underlying security. A warrant generally ceases to have value if it is not exercised prior to its expiration date.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing primarily in equity securities of large capitalization companies in the hope of earning long-term growth of capital.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Performance prior to May 1, 2013 reflects the Fund’s investment performance when managed by a previous sub-adviser pursuant to a substantially similar principal investment strategy. Since May 1, 2013, Loomis, Sayles & Company, L.P. has been responsible for the Fund’s day-to-day portfolio management. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
19.07%	-26.40%
6/30/2009	12/31/2008

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Large Cap Value Fund | Large Cap Value Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.66%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.24%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.90%

1 Year

rr_ExpenseExampleYear01

$ 92

3 Years

rr_ExpenseExampleYear03

287

5 Years

rr_ExpenseExampleYear05

498

10 Years

rr_ExpenseExampleYear10

$ 1,108

2008

rr_AnnualReturn2008

(44.62%)

2009

rr_AnnualReturn2009

33.62%

2010

rr_AnnualReturn2010

14.84%

2011

rr_AnnualReturn2011

(4.42%)

2012

rr_AnnualReturn2012

13.23%

2013

rr_AnnualReturn2013

33.21%

2014

rr_AnnualReturn2014

11.31%

2015

rr_AnnualReturn2015

(4.35%)

2016

rr_AnnualReturn2016

11.62%

2017

rr_AnnualReturn2017

14.60%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

19.07%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(26.40%)

1 Year

rr_AverageAnnualReturnYear01

14.60%

5 Years

rr_AverageAnnualReturnYear05

12.65%

10 Years

rr_AverageAnnualReturnYear10

5.25%

Penn Series Large Cap Value Fund | Russell 1000® Value Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

13.66%

5 Years

rr_AverageAnnualReturnYear05

14.04%

10 Years

rr_AverageAnnualReturnYear10

7.10%

XML

Penn Series Large Core Value Fund

FUND SUMMARY:  LARGE CORE VALUE FUND

Investment Objective

The investment objective of the Large Core Value Fund (the “Fund”) is to seek total return.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Large Core Value Fund Large Core Value Fund
Investment Advisory Fees	0.67%
Distribution (12b-1) Fees	none
Other Expenses	0.23%
Total Annual Fund Operating Expenses	0.90%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Large Core Value Fund | Large Core Value Fund | USD ($)	92	287	498	1,108

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 106% of the average value of its portfolio.

Principal Investment Strategy

The Fund invests primarily in value stocks of large capitalization companies. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities of large capitalization companies. The portfolio managers generally consider large capitalization companies to be those companies having market capitalizations within the range of companies included in the Russell 1000^® Value Index, although the portfolio will generally consist of stocks with a market capitalization equal to or greater than the median market capitalization of companies included in such index. As of March 31, 2018, the capitalization range of the Russell 1000^® Value Index was $571 million to $492 billion, and the median market capitalization was $9.4 billion. Because the Fund’s definition of large capitalization companies is dynamic, it will change with the markets. Value stocks are stocks that, in the opinion of the Sub-Adviser, are inexpensive or undervalued relative to the overall stock market.

The Fund primarily invests in dividend-paying stocks, but may also invest in non-income producing stocks. The Fund may invest in convertible debt securities of any credit quality (including securities rated below investment grade (so-called “junk”)).

The Fund may invest in publicly traded real estate investment trusts (“REITs”). The Fund may invest up to 25% of its total assets in foreign securities, some of which may be located in emerging market countries. Securities of foreign issuers that are represented by American Depositary Receipts (“ADRs”) are not subject to this restriction. The Fund may invest in exchange-traded funds (“ETFs”), a type of pooled investment vehicle, in order to manage cash positions or seek exposure to certain markets or market sectors.

Investment decisions are made primarily on the basis of fundamental research. The Sub-Adviser may consider a company’s earnings or cash flow capabilities, dividend prospects, financial strength, growth potential, the strength of the company’s business franchises and management team, sustainability of a company’s competitiveness, and estimates of a company’s net value when selecting securities. The Sub-Adviser may sell a security when the Sub-Adviser’s price objective for the security is reached, the fundamentals of the company deteriorate, a security’s price falls below acquisition cost or to pursue more attractive investment options.

The Fund may buy and sell portfolio securities actively. If it does, its portfolio turnover rate and transaction costs will rise, which may lower Fund performance.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Convertible Securities Risk.  The possibility that the value of the Fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Depositary Receipt Risk.  The possibility that the Fund’s investments in foreign companies through depositary receipts will expose the Fund to the same risks as direct investment in securities of foreign issuers. In addition, investments in ADRs may be less liquid than the underlying shares in their primary trading market, and the value of securities underlying ADRs may change materially at times when U.S. markets are not open for trading.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

Large-Cap Securities Risk.  The possibility that the Fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Other Investment Company Risk.  The possibility that investments by the Fund in shares of other investment companies will subject the Fund to the risks associated with those investment companies. Fund shareholders will also indirectly bear a proportionate share of any underlying investment company’s fees and expenses in addition to paying the Fund’s expenses.

Portfolio Turnover Risk.  The possibility that the Fund may frequently buy and sell portfolio securities, which may increase transaction costs to the Fund and cause the Fund’s performance to be less than you expect.

REITs Risk.  The possibility that the Fund’s investments in REITs will subject the Fund to the risks associated with the direct ownership of real estate, including fluctuations in the value of underlying properties, changes in interest rates and risks related to general or local economic conditions. REITs are dependent upon management skills and generally may not be diversified. REITs are also subject to heavy cash flow dependency, defaults by borrowers or tenants and self-liquidation.

“Value” Investing Risk.  The possibility that the Fund’s investments in securities believed by the Sub-Adviser to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which the Fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the Fund’s investment style shifts out of favor.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in common stocks in the hope of earning long-term growth of capital and income.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
14.96%	-16.11%
9/30/2009	9/30/2011

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Large Core Value Fund	1 Year	5 Years	Since Inception	Inception Date
Large Core Value Fund	15.21%	12.57%	7.00%	Aug. 25, 2008
Russell 1000® Value Index (reflects no deduction for fees, expenses or taxes)	13.66%	14.04%	9.18%	Aug. 25, 2008

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Large Core Value Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  LARGE CORE VALUE FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Large Core Value Fund (the “Fund”) is to seek total return.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 106% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

106.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund invests primarily in value stocks of large capitalization companies. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities of large capitalization companies. The portfolio managers generally consider large capitalization companies to be those companies having market capitalizations within the range of companies included in the Russell 1000^® Value Index, although the portfolio will generally consist of stocks with a market capitalization equal to or greater than the median market capitalization of companies included in such index. As of March 31, 2018, the capitalization range of the Russell 1000^® Value Index was $571 million to $492 billion, and the median market capitalization was $9.4 billion. Because the Fund’s definition of large capitalization companies is dynamic, it will change with the markets. Value stocks are stocks that, in the opinion of the Sub-Adviser, are inexpensive or undervalued relative to the overall stock market.

The Fund primarily invests in dividend-paying stocks, but may also invest in non-income producing stocks. The Fund may invest in convertible debt securities of any credit quality (including securities rated below investment grade (so-called “junk”)).

The Fund may invest in publicly traded real estate investment trusts (“REITs”). The Fund may invest up to 25% of its total assets in foreign securities, some of which may be located in emerging market countries. Securities of foreign issuers that are represented by American Depositary Receipts (“ADRs”) are not subject to this restriction. The Fund may invest in exchange-traded funds (“ETFs”), a type of pooled investment vehicle, in order to manage cash positions or seek exposure to certain markets or market sectors.

Investment decisions are made primarily on the basis of fundamental research. The Sub-Adviser may consider a company’s earnings or cash flow capabilities, dividend prospects, financial strength, growth potential, the strength of the company’s business franchises and management team, sustainability of a company’s competitiveness, and estimates of a company’s net value when selecting securities. The Sub-Adviser may sell a security when the Sub-Adviser’s price objective for the security is reached, the fundamentals of the company deteriorate, a security’s price falls below acquisition cost or to pursue more attractive investment options.

The Fund may buy and sell portfolio securities actively. If it does, its portfolio turnover rate and transaction costs will rise, which may lower Fund performance.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Convertible Securities Risk.  The possibility that the value of the Fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Depositary Receipt Risk.  The possibility that the Fund’s investments in foreign companies through depositary receipts will expose the Fund to the same risks as direct investment in securities of foreign issuers. In addition, investments in ADRs may be less liquid than the underlying shares in their primary trading market, and the value of securities underlying ADRs may change materially at times when U.S. markets are not open for trading.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

Large-Cap Securities Risk.  The possibility that the Fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Other Investment Company Risk.  The possibility that investments by the Fund in shares of other investment companies will subject the Fund to the risks associated with those investment companies. Fund shareholders will also indirectly bear a proportionate share of any underlying investment company’s fees and expenses in addition to paying the Fund’s expenses.

Portfolio Turnover Risk.  The possibility that the Fund may frequently buy and sell portfolio securities, which may increase transaction costs to the Fund and cause the Fund’s performance to be less than you expect.

REITs Risk.  The possibility that the Fund’s investments in REITs will subject the Fund to the risks associated with the direct ownership of real estate, including fluctuations in the value of underlying properties, changes in interest rates and risks related to general or local economic conditions. REITs are dependent upon management skills and generally may not be diversified. REITs are also subject to heavy cash flow dependency, defaults by borrowers or tenants and self-liquidation.

“Value” Investing Risk.  The possibility that the Fund’s investments in securities believed by the Sub-Adviser to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which the Fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the Fund’s investment style shifts out of favor.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in common stocks in the hope of earning long-term growth of capital and income.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
14.96%	-16.11%
9/30/2009	9/30/2011

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Large Core Value Fund | Large Core Value Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.67%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.23%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.90%

1 Year

rr_ExpenseExampleYear01

$ 92

3 Years

rr_ExpenseExampleYear03

287

5 Years

rr_ExpenseExampleYear05

498

10 Years

rr_ExpenseExampleYear10

$ 1,108

2009

rr_AnnualReturn2009

16.76%

2010

rr_AnnualReturn2010

10.44%

2011

rr_AnnualReturn2011

(4.19%)

2012

rr_AnnualReturn2012

15.58%

2013

rr_AnnualReturn2013

29.78%

2014

rr_AnnualReturn2014

11.29%

2015

rr_AnnualReturn2015

(0.81%)

2016

rr_AnnualReturn2016

9.55%

2017

rr_AnnualReturn2017

15.21%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

14.96%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(16.11%)

1 Year

rr_AverageAnnualReturnYear01

15.21%

5 Years

rr_AverageAnnualReturnYear05

12.57%

Since Inception

rr_AverageAnnualReturnSinceInception

7.00%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Large Core Value Fund | Russell 1000® Value Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

13.66%

5 Years

rr_AverageAnnualReturnYear05

14.04%

Since Inception

rr_AverageAnnualReturnSinceInception

9.18%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

XML

Penn Series Index 500 Fund

FUND SUMMARY:  INDEX 500 FUND

Investment Objective

The investment objective of the Index 500 Fund (the “Fund”) is to seek a total return (capital appreciation and income) which corresponds to that of the S&P 500^® Index.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Index 500 Fund Index 500 Fund
Investment Advisory Fees	0.13%
Distribution (12b-1) Fees	none
Other Expenses	0.23%
Total Annual Fund Operating Expenses	0.36%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Index 500 Fund | Index 500 Fund | USD ($)	37	116	202	456

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 2% of the average value of its portfolio.

Principal Investment Strategy

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities listed in the S&P 500^® Index (the “Index”). Under normal circumstances, however, the Fund intends to invest substantially all of its assets in securities of companies included in the Index and close substitutes (such as index futures contracts) that are designed to track the Index. The Index is a well-known stock market index that includes common stocks of approximately 500 companies from all major industries that measures the performance of the large-cap sector of the market. Stocks in the Index are weighted according to their float adjusted capitalizations. The Fund may concentrate (invest 25% or more of the value of its assets) in the securities of issuers having their principal business activities in the same industry if the Index is also concentrated in such industry.

The Sub-Adviser does not manage the Fund according to traditional methods of “active” investment management, which involve the buying and selling of securities based upon economic, financial and market analysis and investment judgment. Instead, the Sub-Adviser utilizes a “passive” investment approach, attempting to replicate the investment performance of the Index through automated statistical analytic procedures.

The Sub-Adviser seeks to replicate the returns of the Index by investing in the securities of the Index in approximately their Index weight. However, under various circumstances, it may not be possible or practicable to purchase all of those securities in those weightings. In those circumstances, the Fund may purchase a sample of stocks in the Index in proportions expected to match generally the performance of the Index as a whole. In addition, from time to time, stocks are added to or removed from the Index. The Fund may sell stocks that are represented in the Index, or purchase stocks that are not yet represented in the Index, in anticipation of their removal from or addition to the Index.

The Sub-Adviser may at times purchase or sell futures contracts in lieu of investment directly in the stocks making up the Index. The Sub-Adviser might do so, for example, in order to increase the Fund’s investment exposure pending investment of cash in the stocks comprising the Index. Alternatively, the Sub-Adviser might use futures to reduce its investment exposure to the Index in situations where it intends to sell a portion of the stocks in the Fund’s portfolio but the sale has not yet been completed.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Concentration Risk.  The possibility that, to the extent the Fund invests to a significant extent in a particular industry or group of industries within a particular sector, the Fund may be subject to greater risks than if its investments were broadly diversified across industries and sectors. The Fund also is subject to loss due to adverse occurrences that may affect that industry or group of industries.

Counterparty Risk.  The possibility that a party to a transaction involving the Fund may fail to meet its obligations thereby causing the Fund to lose money or the benefit of the transaction or preventing the Fund from selling or buying other securities to implement its investment strategies.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Large-Cap Securities Risk.  The possibility that the Fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Passive Investment Risk.  The possibility that the Fund’s return may be lower than the return of an actively managed fund because the Fund holds shares of a security based on the holdings of its benchmark index, not the current or projected performance of a security, industry or sector. The Fund does not take defensive positions under any market conditions, including declining markets.

Sampling Risk.  The possibility that the Fund may not hold all of the securities included in its benchmark index and that the securities selected for the Fund, in the aggregate, will not provide investment performance matching that of the Fund’s benchmark index.

Tracking Error Risk.  The possibility that the Sub-Adviser may not be able to cause the Fund’s performance to correspond to that of the Index, either on a daily or aggregate basis. Factors such as Fund expenses, imperfect correlation between the Fund’s investments and those of the Index, rounding of share prices, changes to the composition of the Index, regulatory policies, and high portfolio turnover rate all contribute to tracking error. Tracking error may cause the Fund’s performance to be less than you expect.

Unconstrained Sector Risk.  The possibility that the Fund may invest a substantial portion of its assets within one or more economic sectors or industries, which may change from time to time. Greater investment focus on one or more sectors or industries increases the potential for volatility and the risk that events negatively affecting such sectors or industries could reduce returns, potentially causing the value of the Fund’s shares to decrease, perhaps significantly.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in common stocks in the hope of achieving a total return which corresponds to that of the Index.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Performance prior to August 25, 2008 reflects the Fund’s investment performance when managed by a previous sub-adviser pursuant to a substantially similar principal investment strategy. Since August 25, 2008, SSGA Funds Management, Inc. has been responsible for the Fund’s day-to-day portfolio management. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
15.74%	-21.85%
6/30/2009	12/31/2008

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Index 500 Fund	1 Year	5 Years	10 Years
Index 500 Fund	21.50%	15.37%	8.33%
S&P 500® Index (reflects no deduction for fees, expenses or taxes)	21.83%	15.79%	8.50%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Index 500 Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  INDEX 500 FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Index 500 Fund (the “Fund”) is to seek a total return (capital appreciation and income) which corresponds to that of the S&P 500^® Index.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 2% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

2.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities listed in the S&P 500^® Index (the “Index”). Under normal circumstances, however, the Fund intends to invest substantially all of its assets in securities of companies included in the Index and close substitutes (such as index futures contracts) that are designed to track the Index. The Index is a well-known stock market index that includes common stocks of approximately 500 companies from all major industries that measures the performance of the large-cap sector of the market. Stocks in the Index are weighted according to their float adjusted capitalizations. The Fund may concentrate (invest 25% or more of the value of its assets) in the securities of issuers having their principal business activities in the same industry if the Index is also concentrated in such industry.

The Sub-Adviser does not manage the Fund according to traditional methods of “active” investment management, which involve the buying and selling of securities based upon economic, financial and market analysis and investment judgment. Instead, the Sub-Adviser utilizes a “passive” investment approach, attempting to replicate the investment performance of the Index through automated statistical analytic procedures.

The Sub-Adviser seeks to replicate the returns of the Index by investing in the securities of the Index in approximately their Index weight. However, under various circumstances, it may not be possible or practicable to purchase all of those securities in those weightings. In those circumstances, the Fund may purchase a sample of stocks in the Index in proportions expected to match generally the performance of the Index as a whole. In addition, from time to time, stocks are added to or removed from the Index. The Fund may sell stocks that are represented in the Index, or purchase stocks that are not yet represented in the Index, in anticipation of their removal from or addition to the Index.

The Sub-Adviser may at times purchase or sell futures contracts in lieu of investment directly in the stocks making up the Index. The Sub-Adviser might do so, for example, in order to increase the Fund’s investment exposure pending investment of cash in the stocks comprising the Index. Alternatively, the Sub-Adviser might use futures to reduce its investment exposure to the Index in situations where it intends to sell a portion of the stocks in the Fund’s portfolio but the sale has not yet been completed.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund may concentrate (invest 25% or more of the value of its assets) in the securities of issuers having their principal business activities in the same industry if the Index is also concentrated in such industry.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Concentration Risk.  The possibility that, to the extent the Fund invests to a significant extent in a particular industry or group of industries within a particular sector, the Fund may be subject to greater risks than if its investments were broadly diversified across industries and sectors. The Fund also is subject to loss due to adverse occurrences that may affect that industry or group of industries.

Counterparty Risk.  The possibility that a party to a transaction involving the Fund may fail to meet its obligations thereby causing the Fund to lose money or the benefit of the transaction or preventing the Fund from selling or buying other securities to implement its investment strategies.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Large-Cap Securities Risk.  The possibility that the Fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Passive Investment Risk.  The possibility that the Fund’s return may be lower than the return of an actively managed fund because the Fund holds shares of a security based on the holdings of its benchmark index, not the current or projected performance of a security, industry or sector. The Fund does not take defensive positions under any market conditions, including declining markets.

Sampling Risk.  The possibility that the Fund may not hold all of the securities included in its benchmark index and that the securities selected for the Fund, in the aggregate, will not provide investment performance matching that of the Fund’s benchmark index.

Tracking Error Risk.  The possibility that the Sub-Adviser may not be able to cause the Fund’s performance to correspond to that of the Index, either on a daily or aggregate basis. Factors such as Fund expenses, imperfect correlation between the Fund’s investments and those of the Index, rounding of share prices, changes to the composition of the Index, regulatory policies, and high portfolio turnover rate all contribute to tracking error. Tracking error may cause the Fund’s performance to be less than you expect.

Unconstrained Sector Risk.  The possibility that the Fund may invest a substantial portion of its assets within one or more economic sectors or industries, which may change from time to time. Greater investment focus on one or more sectors or industries increases the potential for volatility and the risk that events negatively affecting such sectors or industries could reduce returns, potentially causing the value of the Fund’s shares to decrease, perhaps significantly.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in common stocks in the hope of achieving a total return which corresponds to that of the Index.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Performance prior to August 25, 2008 reflects the Fund’s investment performance when managed by a previous sub-adviser pursuant to a substantially similar principal investment strategy. Since August 25, 2008, SSGA Funds Management, Inc. has been responsible for the Fund’s day-to-day portfolio management. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
15.74%	-21.85%
6/30/2009	12/31/2008

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Index 500 Fund | Index 500 Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.13%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.23%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.36%

1 Year

rr_ExpenseExampleYear01

$ 37

3 Years

rr_ExpenseExampleYear03

116

5 Years

rr_ExpenseExampleYear05

202

10 Years

rr_ExpenseExampleYear10

$ 456

2008

rr_AnnualReturn2008

(36.08%)

2009

rr_AnnualReturn2009

26.11%

2010

rr_AnnualReturn2010

14.77%

2011

rr_AnnualReturn2011

1.76%

2012

rr_AnnualReturn2012

15.68%

2013

rr_AnnualReturn2013

31.87%

2014

rr_AnnualReturn2014

13.25%

2015

rr_AnnualReturn2015

1.00%

2016

rr_AnnualReturn2016

11.52%

2017

rr_AnnualReturn2017

21.50%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

15.74%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(21.85%)

1 Year

rr_AverageAnnualReturnYear01

21.50%

5 Years

rr_AverageAnnualReturnYear05

15.37%

10 Years

rr_AverageAnnualReturnYear10

8.33%

Penn Series Index 500 Fund | S&P 500® Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

21.83%

5 Years

rr_AverageAnnualReturnYear05

15.79%

10 Years

rr_AverageAnnualReturnYear10

8.50%

XML

Penn Series Mid Cap Growth Fund

FUND SUMMARY:  MID CAP GROWTH FUND

Investment Objective

The investment objective of the Mid Cap Growth Fund (the “Fund”) is to maximize capital appreciation.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Mid Cap Growth Fund Mid Cap Growth Fund
Investment Advisory Fees	0.70%
Distribution (12b-1) Fees	none
Other Expenses	0.26%
Total Annual Fund Operating Expenses	0.96%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Mid Cap Growth Fund | Mid Cap Growth Fund | USD ($)	98	306	531	1,178

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 25% of the average value of its portfolio.

Principal Investment Strategy

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of mid-cap companies. For purposes of this policy, mid-capitalization companies have market capitalizations that fall within the market capitalization range of companies in the Russell Midcap^® Growth Index at the time of purchase (as of March 31, 2018, this range was between $1.28 billion and $41.88 billion). Because the Fund’s definition of mid-cap companies is dynamic, the lower and upper limits on market capitalization will change with the markets.

In selecting securities for the Fund, the Sub-Adviser primarily emphasizes a bottom-up (research individual issuers) approach and focuses on companies it believes have the potential for strong growth, increasing profitability, attractive valuations and sound capital structures. The Sub-Adviser may look at a number of factors in its consideration of a company, such as: new or innovative products or services; adaptive or creative management; strong financial and operational capabilities to sustain multi-year growth; stable and consistent revenue, earnings, and cash flow; a strong balance sheet; market potential; and profit potential. Part of the Sub-Adviser’s investment process also includes a review of the macroeconomic environment, with a focus on factors such as interest rates, inflation, consumer confidence and corporate spending.

Generally, in determining whether to sell a security, the Sub-Adviser considers many factors, including what it believes to be excessive valuation given company growth prospects, deterioration of fundamentals, weak cash flow to support shareholder returns, and unexpected and poorly explained management changes. The Sub-Adviser also may sell a security to reduce the Fund’s holding in that security, to take advantage of what it believes are more attractive investment opportunities or to raise cash.

The Fund may have a significant portion of its assets invested in securities of companies conducting business in a broadly related group of industries within one or more economic sectors. While the sectors to which the Fund is exposed are expected to vary over time, as of the date of this Prospectus, the Fund had significant exposure to the Consumer Discretionary, Health Care, Industrials, and Information Technology sectors.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

“Growth” Investing Risk.  The possibility that the Fund’s investments in securities of companies perceived to be “growth” companies may underperform when the Fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Mid-Cap Securities Risk.  The possibility that the return on the Fund’s investments in mid-cap companies may be less than the return on investments in stocks of larger or smaller companies or the stock market as a whole. Mid-cap companies may be more vulnerable to market volatility and adverse business or economic events than larger, more established companies. The securities of mid-cap companies are more likely to trade in lower volumes and are generally subject to greater and less predictable price changes than the securities of larger capitalization companies.

Sector Risk.  At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in a broadly related group of industries within an economic sector. Companies in the same economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments in that economic sector, including adverse market conditions, legislative or regulatory changes, and/or increased competition affecting that sector, than funds that invest more broadly. As of the date of this Prospectus, the Fund had significant exposure to the Consumer Discretionary, Health Care, Industrials, and Information Technology sectors. In addition to these general risks, the sectors specified are also subject to the risks described below.

Consumer Discretionary Sector Risk.  The manufacturing segment of the Consumer Discretionary Sector includes automotive, household durable goods, leisure equipment, and textiles and apparel. The services segment includes restaurants, hotels, and other leisure facilities, media production and services, and consumer retailing and services. The performance of companies operating in this sector has historically been closely tied to the performance of the overall economy, and also is affected by economic growth, consumer confidence, social trends, attitudes and spending. Changes in demographics, disposable income levels, and consumer tastes also can affect the demand for, and success of, consumer products and services in the marketplace. Moreover, the Consumer Discretionary Sector encompasses those businesses that tend to be the most sensitive to economic cycles.

Health Care Sector Risk.  The Health Care Sector includes health care providers and services, companies that manufacture and distribute health care equipment and supplies, and health care technology companies. It also includes companies involved in the research, development, production and marketing of pharmaceuticals and biotechnology products. The prices of the securities of companies operating in this sector are closely tied to government regulation and approval of their products and services, which can have a significant effect on the price and availability of those products and services. This sector also can be significantly affected by, among other things, lapsing patent protection, technological developments that make drugs obsolete, and price controls.

Industrials Sector Risk.  The Industrials Sector includes manufacturers and distributors of capital goods such as aerospace and defense, building projects, electrical equipment and machinery, and companies that offer construction and engineering services. It also includes providers of commercial and professional services including printing, environmental and facilities services, office services and supplies, security and alarm services, human resource and employment services, research and consulting services. This sector also includes companies that provide transportation services. The Industrials Sector can be significantly affected by, among other things, business cycle fluctuations, worldwide economy growth, government and corporate spending, supply and demand for specific products and manufacturing, and government regulation. The prices of the securities of Industrials companies may fluctuate due to the level and volatility of commodity prices, the exchange value of the dollar, import controls, worldwide competition, liability for environmental damage, depletion of resources, and mandated expenditures for safety and pollution control devices.

Information Technology Sector Risk.  The Information Technology Sector includes internet and software companies, companies that offer information technology services, and manufacturers and distributors of technology hardware and equipment, including semiconductors, communications equipment, cellular phones, computers and peripherals, electronic equipment and related instruments. The prices of the securities of these companies are closely tied to market competition, increased sensitivity to short product cycles and aggressive pricing, and problems with bringing products to market.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in mid-cap stocks in the hope of achieving above-average capital appreciation.

Best Quarter	Worst Quarter
22.84%	-28.78%
9/30/2009	12/31/2008

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Mid Cap Growth Fund	1 Year	5 Years	10 Years
Mid Cap Growth Fund	27.08%	13.79%	5.99%
Russell Midcap® Growth Index (reflects no deduction for fees, expenses or taxes)	25.27%	15.30%	9.10%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Mid Cap Growth Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  MID CAP GROWTH FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Mid Cap Growth Fund (the “Fund”) is to maximize capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 25% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

25.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of mid-cap companies. For purposes of this policy, mid-capitalization companies have market capitalizations that fall within the market capitalization range of companies in the Russell Midcap^® Growth Index at the time of purchase (as of March 31, 2018, this range was between $1.28 billion and $41.88 billion). Because the Fund’s definition of mid-cap companies is dynamic, the lower and upper limits on market capitalization will change with the markets.

In selecting securities for the Fund, the Sub-Adviser primarily emphasizes a bottom-up (research individual issuers) approach and focuses on companies it believes have the potential for strong growth, increasing profitability, attractive valuations and sound capital structures. The Sub-Adviser may look at a number of factors in its consideration of a company, such as: new or innovative products or services; adaptive or creative management; strong financial and operational capabilities to sustain multi-year growth; stable and consistent revenue, earnings, and cash flow; a strong balance sheet; market potential; and profit potential. Part of the Sub-Adviser’s investment process also includes a review of the macroeconomic environment, with a focus on factors such as interest rates, inflation, consumer confidence and corporate spending.

Generally, in determining whether to sell a security, the Sub-Adviser considers many factors, including what it believes to be excessive valuation given company growth prospects, deterioration of fundamentals, weak cash flow to support shareholder returns, and unexpected and poorly explained management changes. The Sub-Adviser also may sell a security to reduce the Fund’s holding in that security, to take advantage of what it believes are more attractive investment opportunities or to raise cash.

The Fund may have a significant portion of its assets invested in securities of companies conducting business in a broadly related group of industries within one or more economic sectors. While the sectors to which the Fund is exposed are expected to vary over time, as of the date of this Prospectus, the Fund had significant exposure to the Consumer Discretionary, Health Care, Industrials, and Information Technology sectors.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

“Growth” Investing Risk.  The possibility that the Fund’s investments in securities of companies perceived to be “growth” companies may underperform when the Fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Mid-Cap Securities Risk.  The possibility that the return on the Fund’s investments in mid-cap companies may be less than the return on investments in stocks of larger or smaller companies or the stock market as a whole. Mid-cap companies may be more vulnerable to market volatility and adverse business or economic events than larger, more established companies. The securities of mid-cap companies are more likely to trade in lower volumes and are generally subject to greater and less predictable price changes than the securities of larger capitalization companies.

Sector Risk.  At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in a broadly related group of industries within an economic sector. Companies in the same economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments in that economic sector, including adverse market conditions, legislative or regulatory changes, and/or increased competition affecting that sector, than funds that invest more broadly. As of the date of this Prospectus, the Fund had significant exposure to the Consumer Discretionary, Health Care, Industrials, and Information Technology sectors. In addition to these general risks, the sectors specified are also subject to the risks described below.

Consumer Discretionary Sector Risk.  The manufacturing segment of the Consumer Discretionary Sector includes automotive, household durable goods, leisure equipment, and textiles and apparel. The services segment includes restaurants, hotels, and other leisure facilities, media production and services, and consumer retailing and services. The performance of companies operating in this sector has historically been closely tied to the performance of the overall economy, and also is affected by economic growth, consumer confidence, social trends, attitudes and spending. Changes in demographics, disposable income levels, and consumer tastes also can affect the demand for, and success of, consumer products and services in the marketplace. Moreover, the Consumer Discretionary Sector encompasses those businesses that tend to be the most sensitive to economic cycles.

Health Care Sector Risk.  The Health Care Sector includes health care providers and services, companies that manufacture and distribute health care equipment and supplies, and health care technology companies. It also includes companies involved in the research, development, production and marketing of pharmaceuticals and biotechnology products. The prices of the securities of companies operating in this sector are closely tied to government regulation and approval of their products and services, which can have a significant effect on the price and availability of those products and services. This sector also can be significantly affected by, among other things, lapsing patent protection, technological developments that make drugs obsolete, and price controls.

Industrials Sector Risk.  The Industrials Sector includes manufacturers and distributors of capital goods such as aerospace and defense, building projects, electrical equipment and machinery, and companies that offer construction and engineering services. It also includes providers of commercial and professional services including printing, environmental and facilities services, office services and supplies, security and alarm services, human resource and employment services, research and consulting services. This sector also includes companies that provide transportation services. The Industrials Sector can be significantly affected by, among other things, business cycle fluctuations, worldwide economy growth, government and corporate spending, supply and demand for specific products and manufacturing, and government regulation. The prices of the securities of Industrials companies may fluctuate due to the level and volatility of commodity prices, the exchange value of the dollar, import controls, worldwide competition, liability for environmental damage, depletion of resources, and mandated expenditures for safety and pollution control devices.

Information Technology Sector Risk.  The Information Technology Sector includes internet and software companies, companies that offer information technology services, and manufacturers and distributors of technology hardware and equipment, including semiconductors, communications equipment, cellular phones, computers and peripherals, electronic equipment and related instruments. The prices of the securities of these companies are closely tied to market competition, increased sensitivity to short product cycles and aggressive pricing, and problems with bringing products to market.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in mid-cap stocks in the hope of achieving above-average capital appreciation.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
22.84%	-28.78%
9/30/2009	12/31/2008

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Mid Cap Growth Fund | Mid Cap Growth Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.70%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.26%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.96%

1 Year

rr_ExpenseExampleYear01

$ 98

3 Years

rr_ExpenseExampleYear03

306

5 Years

rr_ExpenseExampleYear05

531

10 Years

rr_ExpenseExampleYear10

$ 1,178

2008

rr_AnnualReturn2008

(48.87%)

2009

rr_AnnualReturn2009

47.79%

2010

rr_AnnualReturn2010

26.84%

2011

rr_AnnualReturn2011

(7.78%)

2012

rr_AnnualReturn2012

6.08%

2013

rr_AnnualReturn2013

36.72%

2014

rr_AnnualReturn2014

9.49%

2015

rr_AnnualReturn2015

(5.78%)

2016

rr_AnnualReturn2016

6.42%

2017

rr_AnnualReturn2017

27.08%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

22.84%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(28.78%)

1 Year

rr_AverageAnnualReturnYear01

27.08%

5 Years

rr_AverageAnnualReturnYear05

13.79%

10 Years

rr_AverageAnnualReturnYear10

5.99%

Penn Series Mid Cap Growth Fund | Russell Midcap® Growth Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

25.27%

5 Years

rr_AverageAnnualReturnYear05

15.30%

10 Years

rr_AverageAnnualReturnYear10

9.10%

XML

Penn Series Mid Cap Value Fund

FUND SUMMARY:  MID CAP VALUE FUND

Investment Objective

The investment objective of the Mid Cap Value Fund (the “Fund”) is to achieve growth of capital.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Mid Cap Value Fund Mid Cap Value Fund
Investment Advisory Fees	0.55%
Distribution (12b-1) Fees	none
Other Expenses	0.23%
Total Annual Fund Operating Expenses	0.78%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Mid Cap Value Fund | Mid Cap Value Fund | USD ($)	80	249	433	966

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 31% of the average value of its portfolio.

Principal Investment Strategy

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of mid-cap companies. For purposes of this policy, mid capitalization companies have market capitalizations that fall within the market capitalization range of companies in the Russell Midcap^® Index at the time of purchase (as of March 31, 2018, this range was between $572 million and $56.3 billion). Because the Fund’s definition of mid-cap companies is dynamic, the lower and upper limits on market capitalization will change with the markets. In selecting individual securities, the Sub-Adviser uses bottom-up, fundamental research to identify high quality companies that are trading at a substantial discount to their intrinsic value, defined as the Sub-Adviser’s estimate of a company’s true long-term economic worth, where there is a strategic plan or event that is expected to both enhance value and narrow the value/price gap. Intrinsic value reflects the Sub-Adviser’s analysis and estimates. There is no guarantee that any intrinsic value will be realized; security prices may decrease regardless of intrinsic values. Applying a consistent, private equity-style investment framework, the Sub-Adviser focuses its research efforts on a company’s long-term outlook and strategic catalysts that can potentially unlock value. Their approach emphasizes asset values and cash flows, directly engaging a company’s management team to evaluate its strategic direction, execution abilities and direct incentive compensation.

The Sub-Adviser will consider reducing or eliminating a position when the gap between its price and its intrinsic value has narrowed or been eliminated or when other opportunities appear more attractive. Changes in management or corporate strategy may also result in the reduction or elimination of a position. The Sub-Adviser does not have an automatic sell decision when a holding increases to a certain market capitalization level or based on underperformance. They would continue to hold a stock if they believed that it could ultimately contribute to performance.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Catalyst Risk.  Investing in companies in anticipation of a catalyst carries the risk that the catalyst may not happen as anticipated, possibly due to the actions of other market participants, or the market may react to the catalyst differently than expected.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Liquidity Risk.   The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Mid-Cap Securities Risk.  The possibility that the return on the Fund’s investments in mid-cap companies may be less than the return on investments in stocks of larger or smaller companies or the stock market as a whole. Mid-cap companies may be more vulnerable to market volatility and adverse business or economic events than larger, more established companies. The securities of mid-cap companies are more likely to trade in lower volumes and are generally subject to greater and less predictable price changes than the securities of larger capitalization companies.

“Value” Investing Risk.  The possibility that the Fund’s investments in securities believed by the Sub-Adviser to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which the Fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the Fund’s investment style shifts out of favor.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in mid-cap stocks in the hope of achieving above-average growth of capital.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
25.30%	-28.74%
9/30/2009	12/31/2008

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Mid Cap Value Fund	1 Year	5 Years	10 Years
Mid Cap Value Fund	17.45%	14.42%	7.51%
Russell Midcap® Value Index (reflects no deduction for fees, expenses or taxes)	13.34%	14.68%	9.10%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Mid Cap Value Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  MID CAP VALUE FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Mid Cap Value Fund (the “Fund”) is to achieve growth of capital.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 31% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

31.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of mid-cap companies. For purposes of this policy, mid capitalization companies have market capitalizations that fall within the market capitalization range of companies in the Russell Midcap^® Index at the time of purchase (as of March 31, 2018, this range was between $572 million and $56.3 billion). Because the Fund’s definition of mid-cap companies is dynamic, the lower and upper limits on market capitalization will change with the markets. In selecting individual securities, the Sub-Adviser uses bottom-up, fundamental research to identify high quality companies that are trading at a substantial discount to their intrinsic value, defined as the Sub-Adviser’s estimate of a company’s true long-term economic worth, where there is a strategic plan or event that is expected to both enhance value and narrow the value/price gap. Intrinsic value reflects the Sub-Adviser’s analysis and estimates. There is no guarantee that any intrinsic value will be realized; security prices may decrease regardless of intrinsic values. Applying a consistent, private equity-style investment framework, the Sub-Adviser focuses its research efforts on a company’s long-term outlook and strategic catalysts that can potentially unlock value. Their approach emphasizes asset values and cash flows, directly engaging a company’s management team to evaluate its strategic direction, execution abilities and direct incentive compensation.

The Sub-Adviser will consider reducing or eliminating a position when the gap between its price and its intrinsic value has narrowed or been eliminated or when other opportunities appear more attractive. Changes in management or corporate strategy may also result in the reduction or elimination of a position. The Sub-Adviser does not have an automatic sell decision when a holding increases to a certain market capitalization level or based on underperformance. They would continue to hold a stock if they believed that it could ultimately contribute to performance.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Catalyst Risk.  Investing in companies in anticipation of a catalyst carries the risk that the catalyst may not happen as anticipated, possibly due to the actions of other market participants, or the market may react to the catalyst differently than expected.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Liquidity Risk.   The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Mid-Cap Securities Risk.  The possibility that the return on the Fund’s investments in mid-cap companies may be less than the return on investments in stocks of larger or smaller companies or the stock market as a whole. Mid-cap companies may be more vulnerable to market volatility and adverse business or economic events than larger, more established companies. The securities of mid-cap companies are more likely to trade in lower volumes and are generally subject to greater and less predictable price changes than the securities of larger capitalization companies.

“Value” Investing Risk.  The possibility that the Fund’s investments in securities believed by the Sub-Adviser to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which the Fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the Fund’s investment style shifts out of favor.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in mid-cap stocks in the hope of achieving above-average growth of capital.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
25.30%	-28.74%
9/30/2009	12/31/2008

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Mid Cap Value Fund | Mid Cap Value Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.55%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.23%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.78%

1 Year

rr_ExpenseExampleYear01

$ 80

3 Years

rr_ExpenseExampleYear03

249

5 Years

rr_ExpenseExampleYear05

433

10 Years

rr_ExpenseExampleYear10

$ 966

2008

rr_AnnualReturn2008

(47.26%)

2009

rr_AnnualReturn2009

46.99%

2010

rr_AnnualReturn2010

25.77%

2011

rr_AnnualReturn2011

(6.27%)

2012

rr_AnnualReturn2012

15.17%

2013

rr_AnnualReturn2013

36.20%

2014

rr_AnnualReturn2014

13.67%

2015

rr_AnnualReturn2015

(7.98%)

2016

rr_AnnualReturn2016

17.20%

2017

rr_AnnualReturn2017

17.45%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

25.30%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(28.74%)

1 Year

rr_AverageAnnualReturnYear01

17.45%

5 Years

rr_AverageAnnualReturnYear05

14.42%

10 Years

rr_AverageAnnualReturnYear10

7.51%

Penn Series Mid Cap Value Fund | Russell Midcap® Value Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

13.34%

5 Years

rr_AverageAnnualReturnYear05

14.68%

10 Years

rr_AverageAnnualReturnYear10

9.10%

XML

Penn Series Mid Core Value Fund

FUND SUMMARY:  MID CORE VALUE FUND

Investment Objective

The investment objective of the Mid Core Value Fund (the “Fund”) is to achieve capital appreciation.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Mid Core Value Fund Mid Core Value Fund
Investment Advisory Fees	0.72%
Distribution (12b-1) Fees	none
Other Expenses	0.30%
Acquired Fund Fees and Expenses	0.01%
Total Annual Fund Operating Expenses	1.03%	[1]

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Mid Core Value Fund | Mid Core Value Fund | USD ($)	105	328	569	1,259

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 45% of the average value of its portfolio.

Principal Investment Strategy

Under normal market conditions, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of medium capitalization companies. For purposes of the Fund’s investments, equity securities include common stock, preferred stock, and equity-equivalent securities, such as convertible securities, stock futures contracts or stock index futures contracts. The Sub-Adviser considers medium size companies whose market capitalization at the time of purchase is within the capitalization range of the Russell 3000^® Index, excluding the largest 100 such companies, for inclusion in the Fund’s portfolio. As of March 31, 2018, this capitalization range was between $7.7 million and $56.7 billion. The Sub-Adviser intends to manage the Fund so that its weighted capitalization falls within the capitalization range of the members of the Russell Midcap^® Index. As of March 31, 2018, this capitalization range was between $571.8 million and $41.9 billion. In selecting stocks for the Fund, the Sub-Adviser looks for companies whose stock price may not reflect the company’s value. The Sub-Adviser attempts to purchase the stocks of these undervalued companies and hold each stock until the price has increased to, or is higher than, a level the Sub-Adviser believes more accurately reflects the fair value of the company. The Fund may invest a portion of its assets in foreign securities when these securities meet the Sub-Adviser’s standards of selection. The Sub-Adviser may sell stocks from the Fund’s portfolio if it believes a stock no longer meets its valuation criteria, a stock’s risk parameters outweigh its return opportunity, more attractive alternatives are identified or specific events alter a stock’s prospects. The Fund may engage in active and frequent trading of portfolio securities in the pursuit of its investment objective.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

IPOs Risk.  The possibility that the Fund’s performance may be affected by the purchase of securities issued in initial public offerings (IPOs) that have little to no trading history, limited issuer information, increased volatility and may not be available to the extent desired. The prices of securities bought in IPOs may rise and fall rapidly, often because of investor perceptions rather than economic reasons.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Mid-Cap Securities Risk.  The possibility that the return on the Fund’s investments in mid-cap companies may be less than the return on investments in stocks of larger or smaller companies or the stock market as a whole. Mid-cap companies may be more vulnerable to market volatility and adverse business or economic events than larger, more established companies. The securities of mid-cap companies are more likely to trade in lower volumes and are generally subject to greater and less predictable price changes than the securities of larger capitalization companies.

Portfolio Turnover Risk.  The possibility that the Fund may frequently buy and sell portfolio securities, which may increase transaction costs to the Fund and cause the Fund’s performance to be less than you expect.

“Value” Investing Risk.  The possibility that the Fund’s investments in securities believed by the Sub-Adviser to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which the Fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the Fund’s investment style shifts out of favor.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in mid-cap stocks in the hope of achieving above-average growth of capital.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Performance prior to May 1, 2013 reflects the Fund’s investment performance when managed by a previous sub-adviser pursuant to a substantially similar principal investment strategy. Since May 1, 2013, American Century Investment Management, Inc. has been responsible for the Fund’s day-to-day portfolio management. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
18.69%	-22.12%
9/30/2009	9/30/2011

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Mid Core Value Fund	1 Year	5 Years	10 Years
Mid Core Value Fund	11.55%	15.18%	8.02%
Russell Midcap® Value Index (reflects no deduction for fees, expenses or taxes)	13.34%	14.68%	9.10%

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Mid Core Value Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  MID CORE VALUE FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Mid Core Value Fund (the “Fund”) is to achieve capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 45% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

45.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund's financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal market conditions, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of medium capitalization companies. For purposes of the Fund’s investments, equity securities include common stock, preferred stock, and equity-equivalent securities, such as convertible securities, stock futures contracts or stock index futures contracts. The Sub-Adviser considers medium size companies whose market capitalization at the time of purchase is within the capitalization range of the Russell 3000^® Index, excluding the largest 100 such companies, for inclusion in the Fund’s portfolio. As of March 31, 2018, this capitalization range was between $7.7 million and $56.7 billion. The Sub-Adviser intends to manage the Fund so that its weighted capitalization falls within the capitalization range of the members of the Russell Midcap^® Index. As of March 31, 2018, this capitalization range was between $571.8 million and $41.9 billion. In selecting stocks for the Fund, the Sub-Adviser looks for companies whose stock price may not reflect the company’s value. The Sub-Adviser attempts to purchase the stocks of these undervalued companies and hold each stock until the price has increased to, or is higher than, a level the Sub-Adviser believes more accurately reflects the fair value of the company. The Fund may invest a portion of its assets in foreign securities when these securities meet the Sub-Adviser’s standards of selection. The Sub-Adviser may sell stocks from the Fund’s portfolio if it believes a stock no longer meets its valuation criteria, a stock’s risk parameters outweigh its return opportunity, more attractive alternatives are identified or specific events alter a stock’s prospects. The Fund may engage in active and frequent trading of portfolio securities in the pursuit of its investment objective.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

IPOs Risk.  The possibility that the Fund’s performance may be affected by the purchase of securities issued in initial public offerings (IPOs) that have little to no trading history, limited issuer information, increased volatility and may not be available to the extent desired. The prices of securities bought in IPOs may rise and fall rapidly, often because of investor perceptions rather than economic reasons.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Mid-Cap Securities Risk.  The possibility that the return on the Fund’s investments in mid-cap companies may be less than the return on investments in stocks of larger or smaller companies or the stock market as a whole. Mid-cap companies may be more vulnerable to market volatility and adverse business or economic events than larger, more established companies. The securities of mid-cap companies are more likely to trade in lower volumes and are generally subject to greater and less predictable price changes than the securities of larger capitalization companies.

Portfolio Turnover Risk.  The possibility that the Fund may frequently buy and sell portfolio securities, which may increase transaction costs to the Fund and cause the Fund’s performance to be less than you expect.

“Value” Investing Risk.  The possibility that the Fund’s investments in securities believed by the Sub-Adviser to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which the Fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the Fund’s investment style shifts out of favor.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in mid-cap stocks in the hope of achieving above-average growth of capital.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Performance prior to May 1, 2013 reflects the Fund’s investment performance when managed by a previous sub-adviser pursuant to a substantially similar principal investment strategy. Since May 1, 2013, American Century Investment Management, Inc. has been responsible for the Fund’s day-to-day portfolio management. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
18.69%	-22.12%
9/30/2009	9/30/2011

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Mid Core Value Fund | Mid Core Value Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.72%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.30%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.03%

^[1]

1 Year

rr_ExpenseExampleYear01

$ 105

3 Years

rr_ExpenseExampleYear03

328

5 Years

rr_ExpenseExampleYear05

569

10 Years

rr_ExpenseExampleYear10

$ 1,259

2008

rr_AnnualReturn2008

(38.89%)

2009

rr_AnnualReturn2009

26.03%

2010

rr_AnnualReturn2010

25.44%

2011

rr_AnnualReturn2011

(3.53%)

2012

rr_AnnualReturn2012

14.46%

2013

rr_AnnualReturn2013

29.15%

2014

rr_AnnualReturn2014

16.37%

2015

rr_AnnualReturn2015

(1.51%)

2016

rr_AnnualReturn2016

22.77%

2017

rr_AnnualReturn2017

11.55%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

18.69%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(22.12%)

1 Year

rr_AverageAnnualReturnYear01

11.55%

5 Years

rr_AverageAnnualReturnYear05

15.18%

10 Years

rr_AverageAnnualReturnYear10

8.02%

Penn Series Mid Core Value Fund | Russell Midcap® Value Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

13.34%

5 Years

rr_AverageAnnualReturnYear05

14.68%

10 Years

rr_AverageAnnualReturnYear10

9.10%

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Penn Series Smid Cap Growth Fund

FUND SUMMARY:  SMID CAP GROWTH FUND

Investment Objective

The investment objective of the SMID Cap Growth Fund (the “Fund”) is to seek long-term growth of capital (capital appreciation).

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Smid Cap Growth Fund Smid Cap Growth Fund
Investment Advisory Fees	0.75%
Distribution (12b-1) Fees	none
Other Expenses	0.29%
Acquired Fund Fees and Expenses	0.01%
Total Annual Fund Operating Expenses	1.05%	[1]
Expense Waivers/Reimbursements and Recapture	0.01%	[2]
Total Annual Fund Operating Expenses (after expense waivers/reimbursements and recapture)	1.06%	[2]

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Smid Cap Growth Fund | Smid Cap Growth Fund | USD ($)	108	335	580	1,283

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 68% of the average value of its portfolio.

Principal Investment Strategy

The Fund attempts to achieve its investment objective by investing primarily in common stocks of small and medium capitalization U.S. companies. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities of small and medium capitalization companies. For purposes of this policy, small and medium capitalization companies have market capitalizations that fall within the outside range of the market capitalizations of companies in the Russell 2000^® Growth Index and the Russell Midcap^® Growth Index at the time of purchase (as of March 31, 2018, this range was between $8 million and $19.44 billion). Because the Fund’s definition of small and medium capitalization companies is dynamic, the lower and upper limits on market capitalization will change with the markets. If the market capitalization of a company held by the Fund moves outside the range, the Fund may, but is not required to, sell the security. The Fund’s investments in small capitalization companies may include micro-capitalization companies. Although the Fund invests primarily in publicly traded U.S. securities, the Fund may invest up to 25% of its net assets in foreign securities, including securities of issuers in countries with emerging markets or economies and securities quoted in foreign currencies. The Fund may also invest in privately held companies and companies that only recently began to trade publicly.

The Sub-Adviser on behalf of the Fund employs a fundamental equity growth investment process that involves evaluating potential investments based on specific characteristics believed to indicate a high-quality business with sustainable growth, including strong business franchises, favorable long-term prospects, and excellent management. The Sub-Adviser will also consider valuation of companies when determining whether to buy and/or sell securities. With respect to the valuation of any private companies held by the Fund, the Sub-Adviser will consider a variety of factors it deems appropriate and reliable, including but not limited to, analyses of valuations of publicly traded companies in a similar line of business. The Sub-Adviser may decide to sell a position for various reasons, including when a company’s fundamental outlook deteriorates, because of valuation and price considerations, for risk management purposes, or when a company is deemed to be misallocating capital or a company no longer fits within the Fund’s definition of a small or medium capitalization company.

The Fund may also invest in American Depositary Receipts (“ADRs”), real estate investment trusts (“REITs”), shares of other investment companies and exchange-traded funds (“ETFs”), derivatives, such as futures, options, and swap agreements, and fixed income securities, such as government, corporate and bank debt obligations.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Depositary Receipt Risk.  The possibility that the Fund’s investments in foreign companies through depositary receipts will expose the Fund to the same risks as direct investment in securities of foreign issuers. In addition, investments in ADRs may be less liquid than the underlying shares in their primary trading market, and the value of securities underlying ADRs may change materially at times when U.S. markets are not open for trading.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that the Fund’s investments in securities of companies perceived to be “growth” companies may underperform when the Fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Micro-Cap Securities Risk.  The possibility that the return on the Fund’s investments in micro-cap companies may be less than the return on investments in stocks of larger companies or the stock market as a whole. Stock prices of micro-cap companies may be based in substantial part on future expectations rather than current achievements and may move sharply, especially during market upturns and downturns. Micro-cap companies are followed by relatively few securities analysts, and there tends to be less publicly available information about these companies. Micro-cap companies are more likely to be newly formed or in the early stages of development, depend on a few key employees, and have relatively limited product lines, markets or financial resources compared to larger capitalization companies.

Other Investment Company Risk.  The possibility that investments by the Fund in shares of other investment companies will subject the Fund to the risks associated with those investment companies. Fund shareholders will also indirectly bear a proportionate share of any underlying investment company’s fees and expenses in addition to paying the Fund’s expenses.

REITs Risk.  The possibility that the Fund’s investments in REITs will subject the Fund to the risks associated with the direct ownership of real estate, including fluctuations in the value of underlying properties, changes in interest rates and risks related to general or local economic conditions. REITs are dependent upon management skills and generally may not be diversified. REITs are also subject to heavy cash flow dependency, defaults by borrowers or tenants and self-liquidation.

Small- and Mid-Cap Securities Risk.  The possibility that the Fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and the Fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in common stocks in the hope of earning long-term returns.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Performance prior to December 1, 2016 reflects the Fund’s investment performance when managed by a previous sub-adviser pursuant to a substantially similar principal investment strategy. Since December 1, 2016, Goldman Sachs Asset Management, L.P. has been responsible for the Fund’s day-to-day portfolio management. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
21.48%	-19.83%
6/30/2009	9/30/2011

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Smid Cap Growth Fund	1 Year	5 Years	Since Inception	Inception Date
Smid Cap Growth Fund	27.56%	13.92%	10.93%	Aug. 25, 2008
Russell 2500® Growth Index (reflects no deduction for fees, expenses or taxes)	24.46%	15.47%	11.13%	Aug. 25, 2008

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund's financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

[2] The “Recapture” amount represents the Fund’s reimbursement of the Adviser for previously waived fees and/or expenses reimbursed by the Adviser. Penn Mutual and the Adviser have contractually agreed to waive a portion of their fees and/or reimburse expenses to the extent necessary to keep the Fund’s Total Annual Operating Expenses from exceeding 1.07% of average daily net assets (excluding nonrecurring account fees, fees on portfolio transactions, such as exchange fees, dividends and interest on securities sold short, acquired fund fees and expenses, service fees, interest, taxes, brokerage commissions, other expenditures which are capitalized in accordance with generally accepted accounting principles, and other non-routine expenses or extraordinary expenses not incurred in the ordinary course of the Fund’s business) through April 30, 2019. The agreement may be terminated prior to April 30, 2019 only by a majority vote of the Company’s Board of Directors for any reason and at any time. Under this agreement, to the extent Penn Mutual and the Adviser do not have an obligation to waive fees and/or reimburse expenses of the Fund (e.g., the Fund is operating at or below its expense limitation), Penn Mutual and the Adviser may seek reimbursement from the Fund for amounts previously waived or reimbursed by Penn Mutual and the Adviser, if any, during the Fund’s preceding three years, but limited to the lesser of (1) the expense cap in effect at the time of the waiver or reimbursement and (2) the expense cap in effect at the time of recapture. Penn Mutual and the Adviser, however, shall not be entitled to any reimbursement that would cause the Fund to exceed its expense limitation.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Smid Cap Growth Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  SMID CAP GROWTH FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the SMID Cap Growth Fund (the “Fund”) is to seek long-term growth of capital (capital appreciation).

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

April 30, 2019

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 68% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

68.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund's financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund attempts to achieve its investment objective by investing primarily in common stocks of small and medium capitalization U.S. companies. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities of small and medium capitalization companies. For purposes of this policy, small and medium capitalization companies have market capitalizations that fall within the outside range of the market capitalizations of companies in the Russell 2000^® Growth Index and the Russell Midcap^® Growth Index at the time of purchase (as of March 31, 2018, this range was between $8 million and $19.44 billion). Because the Fund’s definition of small and medium capitalization companies is dynamic, the lower and upper limits on market capitalization will change with the markets. If the market capitalization of a company held by the Fund moves outside the range, the Fund may, but is not required to, sell the security. The Fund’s investments in small capitalization companies may include micro-capitalization companies. Although the Fund invests primarily in publicly traded U.S. securities, the Fund may invest up to 25% of its net assets in foreign securities, including securities of issuers in countries with emerging markets or economies and securities quoted in foreign currencies. The Fund may also invest in privately held companies and companies that only recently began to trade publicly.

The Sub-Adviser on behalf of the Fund employs a fundamental equity growth investment process that involves evaluating potential investments based on specific characteristics believed to indicate a high-quality business with sustainable growth, including strong business franchises, favorable long-term prospects, and excellent management. The Sub-Adviser will also consider valuation of companies when determining whether to buy and/or sell securities. With respect to the valuation of any private companies held by the Fund, the Sub-Adviser will consider a variety of factors it deems appropriate and reliable, including but not limited to, analyses of valuations of publicly traded companies in a similar line of business. The Sub-Adviser may decide to sell a position for various reasons, including when a company’s fundamental outlook deteriorates, because of valuation and price considerations, for risk management purposes, or when a company is deemed to be misallocating capital or a company no longer fits within the Fund’s definition of a small or medium capitalization company.

The Fund may also invest in American Depositary Receipts (“ADRs”), real estate investment trusts (“REITs”), shares of other investment companies and exchange-traded funds (“ETFs”), derivatives, such as futures, options, and swap agreements, and fixed income securities, such as government, corporate and bank debt obligations.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Depositary Receipt Risk.  The possibility that the Fund’s investments in foreign companies through depositary receipts will expose the Fund to the same risks as direct investment in securities of foreign issuers. In addition, investments in ADRs may be less liquid than the underlying shares in their primary trading market, and the value of securities underlying ADRs may change materially at times when U.S. markets are not open for trading.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that the Fund’s investments in securities of companies perceived to be “growth” companies may underperform when the Fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Micro-Cap Securities Risk.  The possibility that the return on the Fund’s investments in micro-cap companies may be less than the return on investments in stocks of larger companies or the stock market as a whole. Stock prices of micro-cap companies may be based in substantial part on future expectations rather than current achievements and may move sharply, especially during market upturns and downturns. Micro-cap companies are followed by relatively few securities analysts, and there tends to be less publicly available information about these companies. Micro-cap companies are more likely to be newly formed or in the early stages of development, depend on a few key employees, and have relatively limited product lines, markets or financial resources compared to larger capitalization companies.

Other Investment Company Risk.  The possibility that investments by the Fund in shares of other investment companies will subject the Fund to the risks associated with those investment companies. Fund shareholders will also indirectly bear a proportionate share of any underlying investment company’s fees and expenses in addition to paying the Fund’s expenses.

REITs Risk.  The possibility that the Fund’s investments in REITs will subject the Fund to the risks associated with the direct ownership of real estate, including fluctuations in the value of underlying properties, changes in interest rates and risks related to general or local economic conditions. REITs are dependent upon management skills and generally may not be diversified. REITs are also subject to heavy cash flow dependency, defaults by borrowers or tenants and self-liquidation.

Small- and Mid-Cap Securities Risk.  The possibility that the Fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and the Fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in common stocks in the hope of earning long-term returns.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Performance prior to December 1, 2016 reflects the Fund’s investment performance when managed by a previous sub-adviser pursuant to a substantially similar principal investment strategy. Since December 1, 2016, Goldman Sachs Asset Management, L.P. has been responsible for the Fund’s day-to-day portfolio management. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
21.48%	-19.83%
6/30/2009	9/30/2011

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Smid Cap Growth Fund | Smid Cap Growth Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.75%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.29%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.05%

^[1]

Expense Waivers/Reimbursements and Recapture

rr_FeeWaiverOrReimbursementOverAssets

0.01%

^[2]

Total Annual Fund Operating Expenses (after expense waivers/reimbursements and recapture)

rr_NetExpensesOverAssets

1.06%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 108

3 Years

rr_ExpenseExampleYear03

335

5 Years

rr_ExpenseExampleYear05

580

10 Years

rr_ExpenseExampleYear10

$ 1,283

2009

rr_AnnualReturn2009

54.15%

2010

rr_AnnualReturn2010

24.85%

2011

rr_AnnualReturn2011

(4.72%)

2012

rr_AnnualReturn2012

15.35%

2013

rr_AnnualReturn2013

42.84%

2014

rr_AnnualReturn2014

0.61%

2015

rr_AnnualReturn2015

(1.52%)

2016

rr_AnnualReturn2016

6.27%

2017

rr_AnnualReturn2017

27.56%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

21.48%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(19.83%)

1 Year

rr_AverageAnnualReturnYear01

27.56%

5 Years

rr_AverageAnnualReturnYear05

13.92%

Since Inception

rr_AverageAnnualReturnSinceInception

10.93%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Smid Cap Growth Fund | Russell 2500® Growth Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

24.46%

5 Years

rr_AverageAnnualReturnYear05

15.47%

Since Inception

rr_AverageAnnualReturnSinceInception

11.13%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund's financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

[2] The “Recapture” amount represents the Fund’s reimbursement of the Adviser for previously waived fees and/or expenses reimbursed by the Adviser. Penn Mutual and the Adviser have contractually agreed to waive a portion of their fees and/or reimburse expenses to the extent necessary to keep the Fund’s Total Annual Operating Expenses from exceeding 1.07% of average daily net assets (excluding nonrecurring account fees, fees on portfolio transactions, such as exchange fees, dividends and interest on securities sold short, acquired fund fees and expenses, service fees, interest, taxes, brokerage commissions, other expenditures which are capitalized in accordance with generally accepted accounting principles, and other non-routine expenses or extraordinary expenses not incurred in the ordinary course of the Fund’s business) through April 30, 2019. The agreement may be terminated prior to April 30, 2019 only by a majority vote of the Company’s Board of Directors for any reason and at any time. Under this agreement, to the extent Penn Mutual and the Adviser do not have an obligation to waive fees and/or reimburse expenses of the Fund (e.g., the Fund is operating at or below its expense limitation), Penn Mutual and the Adviser may seek reimbursement from the Fund for amounts previously waived or reimbursed by Penn Mutual and the Adviser, if any, during the Fund’s preceding three years, but limited to the lesser of (1) the expense cap in effect at the time of the waiver or reimbursement and (2) the expense cap in effect at the time of recapture. Penn Mutual and the Adviser, however, shall not be entitled to any reimbursement that would cause the Fund to exceed its expense limitation.

XML

Penn Series Smid Cap Value Fund

FUND SUMMARY:  SMID CAP VALUE FUND

Investment Objective

The investment objective of the SMID Cap Value Fund (the “Fund”) is to seek long-term growth of capital.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Smid Cap Value Fund Smid Cap Value Fund
Investment Advisory Fees	0.84%
Distribution (12b-1) Fees	none
Other Expenses	0.26%
Total Annual Fund Operating Expenses	1.10%	[1]

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Smid Cap Value Fund | Smid Cap Value Fund | USD ($)	112	350	606	1,340

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 37% of the average value of its portfolio.

Principal Investment Strategy

The Fund invests primarily in a diversified portfolio of equity securities of small and medium capitalization U.S. companies, generally representing 60 to 125 companies. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities of small and medium capitalization companies. For this Fund, small and medium capitalization companies are those that, at the time of investment, fall within the capitalization range between the smallest company in the Russell 2500™ Value Index (as of March 31, 2018, this amount was $857 million) and the greater of $5 billion or the market capitalization of the largest company in the Russell 2500™ Value Index (as of March 31, 2018, this amount was $12 billion). Because the Fund’s definition of small and medium capitalization companies is dynamic, the lower and upper limits on market capitalization will change with the markets. The Fund’s investments in small capitalization companies may include micro-capitalization companies.

The Fund invests in companies that are determined by the Sub-Adviser to be undervalued, using its fundamental value approach. In selecting securities for the Fund, the Sub-Adviser uses its fundamental research to identify companies whose long-term earnings power is not reflected in the current market price of their securities. The Sub-Adviser’s fundamental value approach to equity investing generally defines value as the relationship between a security’s current price and its intrinsic economic value, as measured by long-term earnings prospects.

To the extent that companies involved in certain industries may from time to time constitute a material portion of the universe of small and medium capitalization companies, the Fund may also invest significantly in these industries (but not more than 25% of its total assets in any one industry). The Fund may invest in American Depositary Receipts (“ADRs”) and non-U.S. securities.

The Sub-Adviser will generally sell a security when it reaches fair value on a risk-adjusted basis. Typically, growth in the size of a company’s market capitalization relative to other domestically traded companies will not cause the Sub-Adviser to dispose of the security.

The Fund may invest in securities issued by non-U.S. companies and enter into forward commitments.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Depositary Receipt Risk.  The possibility that the Fund’s investments in foreign companies through depositary receipts will expose the Fund to the same risks as direct investment in securities of foreign issuers. In addition, investments in ADRs may be less liquid than the underlying shares in their primary trading market, and the value of securities underlying ADRs may change materially at times when U.S. markets are not open for trading.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

Forward Commitment Risk.  The possibility that the Fund engages in when-issued, delayed delivery or forward commitment transactions (e.g., TBAs) and a counterparty fails to consummate the sale, resulting in a missed opportunity by the Fund to obtain an advantageous price or yield. Such transactions may also have the effect of leverage on the Fund and may cause the Fund to be more volatile. Additionally, these transactions may create a higher portfolio turnover rate.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Small- and Mid-Cap Securities Risk.  The possibility that the Fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and the Fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

“Value” Investing Risk. The possibility that the Fund’s investments in securities believed by the Sub-Adviser to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which the Fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the Fund’s investment style shifts out of favor.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in common stocks in the hope of long-term growth of capital.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
24.07%	-22.52%
9/30/2009	9/30/2011

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Smid Cap Value Fund	1 Year	5 Years	Since Inception	Inception Date
Smid Cap Value Fund	13.00%	15.00%	11.66%	Aug. 25, 2008
Russell 2500™ Value Index (reflects no deduction for fees, expenses or taxes)	10.36%	13.27%	9.91%	Aug. 25, 2008

[1] The expense information in the fee table has been restated to reflect a reduction in the Fund's Investment Advisory Fee rate, effective October 1, 2017. As such, the Total Annual Fund Operating Expenses may not correlate to the expense ratios in the Fund's financial highlights and financial statements, which include the prior Investment Advisory Fee rate.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Smid Cap Value Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  SMID CAP VALUE FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the SMID Cap Value Fund (the “Fund”) is to seek long-term growth of capital.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 37% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

37.00%

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

The expense information in the fee table has been restated to reflect a reduction in the Fund's Investment Advisory Fee rate, effective October 1, 2017.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund invests primarily in a diversified portfolio of equity securities of small and medium capitalization U.S. companies, generally representing 60 to 125 companies. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities of small and medium capitalization companies. For this Fund, small and medium capitalization companies are those that, at the time of investment, fall within the capitalization range between the smallest company in the Russell 2500™ Value Index (as of March 31, 2018, this amount was $857 million) and the greater of $5 billion or the market capitalization of the largest company in the Russell 2500™ Value Index (as of March 31, 2018, this amount was $12 billion). Because the Fund’s definition of small and medium capitalization companies is dynamic, the lower and upper limits on market capitalization will change with the markets. The Fund’s investments in small capitalization companies may include micro-capitalization companies.

The Fund invests in companies that are determined by the Sub-Adviser to be undervalued, using its fundamental value approach. In selecting securities for the Fund, the Sub-Adviser uses its fundamental research to identify companies whose long-term earnings power is not reflected in the current market price of their securities. The Sub-Adviser’s fundamental value approach to equity investing generally defines value as the relationship between a security’s current price and its intrinsic economic value, as measured by long-term earnings prospects.

To the extent that companies involved in certain industries may from time to time constitute a material portion of the universe of small and medium capitalization companies, the Fund may also invest significantly in these industries (but not more than 25% of its total assets in any one industry). The Fund may invest in American Depositary Receipts (“ADRs”) and non-U.S. securities.

The Sub-Adviser will generally sell a security when it reaches fair value on a risk-adjusted basis. Typically, growth in the size of a company’s market capitalization relative to other domestically traded companies will not cause the Sub-Adviser to dispose of the security.

The Fund may invest in securities issued by non-U.S. companies and enter into forward commitments.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Depositary Receipt Risk.  The possibility that the Fund’s investments in foreign companies through depositary receipts will expose the Fund to the same risks as direct investment in securities of foreign issuers. In addition, investments in ADRs may be less liquid than the underlying shares in their primary trading market, and the value of securities underlying ADRs may change materially at times when U.S. markets are not open for trading.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

Forward Commitment Risk.  The possibility that the Fund engages in when-issued, delayed delivery or forward commitment transactions (e.g., TBAs) and a counterparty fails to consummate the sale, resulting in a missed opportunity by the Fund to obtain an advantageous price or yield. Such transactions may also have the effect of leverage on the Fund and may cause the Fund to be more volatile. Additionally, these transactions may create a higher portfolio turnover rate.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Small- and Mid-Cap Securities Risk.  The possibility that the Fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and the Fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

“Value” Investing Risk. The possibility that the Fund’s investments in securities believed by the Sub-Adviser to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which the Fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the Fund’s investment style shifts out of favor.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in common stocks in the hope of long-term growth of capital.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
24.07%	-22.52%
9/30/2009	9/30/2011

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Smid Cap Value Fund | Smid Cap Value Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.84%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.26%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.10%

^[1]

1 Year

rr_ExpenseExampleYear01

$ 112

3 Years

rr_ExpenseExampleYear03

350

5 Years

rr_ExpenseExampleYear05

606

10 Years

rr_ExpenseExampleYear10

$ 1,340

2009

rr_AnnualReturn2009

45.59%

2010

rr_AnnualReturn2010

26.87%

2011

rr_AnnualReturn2011

(7.17%)

2012

rr_AnnualReturn2012

18.95%

2013

rr_AnnualReturn2013

38.00%

2014

rr_AnnualReturn2014

9.25%

2015

rr_AnnualReturn2015

(5.69%)

2016

rr_AnnualReturn2016

25.20%

2017

rr_AnnualReturn2017

13.00%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

24.07%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(22.52%)

1 Year

rr_AverageAnnualReturnYear01

13.00%

5 Years

rr_AverageAnnualReturnYear05

15.00%

Since Inception

rr_AverageAnnualReturnSinceInception

11.66%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Smid Cap Value Fund | Russell 2500™ Value Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

10.36%

5 Years

rr_AverageAnnualReturnYear05

13.27%

Since Inception

rr_AverageAnnualReturnSinceInception

9.91%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

[1] The expense information in the fee table has been restated to reflect a reduction in the Fund's Investment Advisory Fee rate, effective October 1, 2017. As such, the Total Annual Fund Operating Expenses may not correlate to the expense ratios in the Fund's financial highlights and financial statements, which include the prior Investment Advisory Fee rate.

XML

Penn Series Small Cap Growth Fund

FUND SUMMARY:  SMALL CAP GROWTH FUND

Investment Objective

The investment objective of the Small Cap Growth Fund (the “Fund”) is capital appreciation.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Small Cap Growth Fund Small Cap Growth Fund
Investment Advisory Fees	0.74%
Distribution (12b-1) Fees	none
Other Expenses	0.27%
Total Annual Fund Operating Expenses	1.01%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Small Cap Growth Fund | Small Cap Growth Fund | USD ($)	103	322	558	1,236

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 25% of the average value of its portfolio.

Principal Investment Strategy

The Fund seeks to achieve capital appreciation by investing, under normal circumstances, at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of small capitalization companies with public stock market capitalizations (based upon shares available for trading on an unrestricted basis) within the range of the market capitalization of companies constituting the Russell 2000^® Growth Index at the time of investment. The small capitalization companies in which the Fund invests are selected for their growth potential. The Fund’s investments in small capitalization companies may include micro-capitalization companies.

The Sub-Adviser applies a “bottom up” approach in choosing investments. In other words, the Sub-Adviser looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

“Growth” Investing Risk.  The possibility that the Fund’s investments in securities of companies perceived to be “growth” companies may underperform when the Fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

IPOs Risk.  The possibility that the Fund’s performance may be affected by the purchase of securities issued in initial public offerings (IPOs) that have little to no trading history, limited issuer information, increased volatility and may not be available to the extent desired. The prices of securities bought in IPOs may rise and fall rapidly, often because of investor perceptions rather than economic reasons.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Small-Cap Securities Risk.  The possibility that the return on the Fund’s investments in small-cap companies may trail the return on investments in stocks of larger companies or the stock market as a whole. Stock prices of smaller companies may be based in substantial part on future expectations rather than current achievements and may move sharply, especially during market upturns and downturns. Small-cap companies generally depend on a few key employees and have relatively limited product lines, markets or financial resources compared to larger capitalization companies.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in small cap growth companies in the hope of earning capital appreciation.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Performance prior to May 1, 2013 reflects the Fund’s investment performance when managed by a previous sub-adviser pursuant to a substantially similar principal investment strategy. Since May 1, 2013, Janus Capital Management LLC has been responsible for the Fund’s day-to-day portfolio management. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
34.99%	-28.98%
6/30/2009	12/31/2008

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Small Cap Growth Fund	1 Year	5 Years	10 Years
Small Cap Growth Fund	24.84%	15.11%	6.01%
Russell 2000® Growth Index (reflects no deduction for fees, expenses or taxes)	22.17%	15.21%	9.19%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Small Cap Growth Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  SMALL CAP GROWTH FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Small Cap Growth Fund (the “Fund”) is capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 25% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

25.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund seeks to achieve capital appreciation by investing, under normal circumstances, at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of small capitalization companies with public stock market capitalizations (based upon shares available for trading on an unrestricted basis) within the range of the market capitalization of companies constituting the Russell 2000^® Growth Index at the time of investment. The small capitalization companies in which the Fund invests are selected for their growth potential. The Fund’s investments in small capitalization companies may include micro-capitalization companies.

The Sub-Adviser applies a “bottom up” approach in choosing investments. In other words, the Sub-Adviser looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

“Growth” Investing Risk.  The possibility that the Fund’s investments in securities of companies perceived to be “growth” companies may underperform when the Fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

IPOs Risk.  The possibility that the Fund’s performance may be affected by the purchase of securities issued in initial public offerings (IPOs) that have little to no trading history, limited issuer information, increased volatility and may not be available to the extent desired. The prices of securities bought in IPOs may rise and fall rapidly, often because of investor perceptions rather than economic reasons.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Small-Cap Securities Risk.  The possibility that the return on the Fund’s investments in small-cap companies may trail the return on investments in stocks of larger companies or the stock market as a whole. Stock prices of smaller companies may be based in substantial part on future expectations rather than current achievements and may move sharply, especially during market upturns and downturns. Small-cap companies generally depend on a few key employees and have relatively limited product lines, markets or financial resources compared to larger capitalization companies.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in small cap growth companies in the hope of earning capital appreciation.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Performance prior to May 1, 2013 reflects the Fund’s investment performance when managed by a previous sub-adviser pursuant to a substantially similar principal investment strategy. Since May 1, 2013, Janus Capital Management LLC has been responsible for the Fund’s day-to-day portfolio management. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
34.99%	-28.98%
6/30/2009	12/31/2008

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Small Cap Growth Fund | Small Cap Growth Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.74%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.27%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.01%

1 Year

rr_ExpenseExampleYear01

$ 103

3 Years

rr_ExpenseExampleYear03

322

5 Years

rr_ExpenseExampleYear05

558

10 Years

rr_ExpenseExampleYear10

$ 1,236

2008

rr_AnnualReturn2008

(50.05%)

2009

rr_AnnualReturn2009

58.65%

2010

rr_AnnualReturn2010

19.13%

2011

rr_AnnualReturn2011

(11.11%)

2012

rr_AnnualReturn2012

5.73%

2013

rr_AnnualReturn2013

37.60%

2014

rr_AnnualReturn2014

7.76%

2015

rr_AnnualReturn2015

0.42%

2016

rr_AnnualReturn2016

8.71%

2017

rr_AnnualReturn2017

24.84%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

34.99%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(28.98%)

1 Year

rr_AverageAnnualReturnYear01

24.84%

5 Years

rr_AverageAnnualReturnYear05

15.11%

10 Years

rr_AverageAnnualReturnYear10

6.01%

Penn Series Small Cap Growth Fund | Russell 2000® Growth Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

22.17%

5 Years

rr_AverageAnnualReturnYear05

15.21%

10 Years

rr_AverageAnnualReturnYear10

9.19%

XML

Penn Series Small Cap Value Fund

FUND SUMMARY:  SMALL CAP VALUE FUND

Investment Objective

The investment objective of the Small Cap Value Fund (the “Fund”) is to seek capital appreciation.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Small Cap Value Fund Small Cap Value Fund
Investment Advisory Fees	0.72%
Distribution (12b-1) Fees	none
Other Expenses	0.25%
Acquired Fund Fees and Expenses	0.01%
Total Annual Fund Operating Expenses	0.98%	[1]

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Small Cap Value Fund | Small Cap Value Fund | USD ($)	100	312	542	1,201

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 59% of the average value of its portfolio.

Principal Investment Strategy

The Fund is managed using a value oriented approach. The Sub-Adviser evaluates securities using fundamental analysis and intends to purchase equity investments that are, in its view, underpriced relative to a combination of such companies’ long term earnings prospects, growth rate, free cash flow and/or dividend-paying ability. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in a diversified portfolio of equity investments in small-cap issuers with public stock market capitalizations (measured at the time of purchase) within the range of the market capitalization of companies constituting the Russell 2000^® Value Index at the time of investment (as of March 31, 2018, this range was between $8 million and $8.44 billion). If the market capitalization of a company held by the Fund moves outside this range, the Fund may, but is not required to, sell the securities. Because the Fund’s definition of small-cap issuers is dynamic, the lower and upper limits on market capitalization will change with the markets. The Fund’s investments in small capitalization companies may include micro-capitalization companies and “unseasoned companies,” which are companies that (together with their predecessors) have operated for less than three years. The Russell 2000^® Value Index measures the performance of those Russell 2000 companies with lower price to book ratio and lower forecasted growth values. Through fundamental proprietary research the Fund will attempt to take advantage of what the Sub-Adviser believes to be well-positioned cash generating businesses run by shareholder-orientated managements. The Sub-Adviser will seek to buy these companies opportunistically at a price low enough to provide a healthy margin of safety. Under normal circumstances, the Fund’s investment horizons for ownership of stocks will be two to three years.

Although the Fund will invest primarily in publicly traded U.S. securities, including real estate investment trusts (“REITs”), it may invest up to 25% of its net assets in foreign securities, including securities of issuers in emerging countries and securities quoted in foreign currencies. The Fund may, but is not required to, undertake hedging activities and may invest in certain instruments, such as forward currency exchange contracts, and may use certain techniques to hedge currency risks associated with the purchase of individual securities denominated in a foreign currency. The Fund may invest in the aggregate up to 20% of its net assets in companies with public stock market capitalizations outside the range of companies constituting the Russell 2000^® Value Index at the time of investment and in fixed income securities, such as government, corporate, and bank debt obligations.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by the Fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

Interest Rate Risk.  The possibility that the prices of the Fund’s fixed income investments will decline due to rising interest rates.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Micro-Cap Securities Risk.  The possibility that the return on the Fund’s investments in micro-cap companies may be less than the return on investments in stocks of larger companies or the stock market as a whole. Stock prices of micro-cap companies may be based in substantial part on future expectations rather than current achievements and may move sharply, especially during market upturns and downturns. Micro-cap companies are followed by relatively few securities analysts, and there tends to be less publicly available information about these companies. Micro-cap companies are more likely to be newly formed or in the early stages of development, depend on a few key employees, and have relatively limited product lines, markets or financial resources compared to larger capitalization companies.

REITs Risk.  The possibility that the Fund’s investments in REITs will subject the Fund to the risks associated with the direct ownership of real estate, including fluctuations in the value of underlying properties, changes in interest rates and risks related to general or local economic conditions. REITs are dependent upon management skills and generally may not be diversified. REITs are also subject to heavy cash flow dependency, defaults by borrowers or tenants and self-liquidation.

Small- and Mid-Cap Securities Risk.  The possibility that the Fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and the Fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

Unseasoned Company Risk.  The possibility that the Fund’s investment in relatively new or unseasoned companies that are in their early stages of development may expose the Fund to greater risks than investments in more established companies with more extensive financial histories and greater liquidity. Unseasoned companies do not have proven track records and may lack substantial capital reserves.

“Value” Investing Risk.  The possibility that the Fund’s investments in securities believed by the Sub-Adviser to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which the Fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the Fund’s investment style shifts out of favor.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in small-cap stocks in the hope of earning above-average capital appreciation.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
19.74%	-25.20%
09/30/2009	12/31/2008

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Small Cap Value Fund	1 Year	5 Years	10 Years
Small Cap Value Fund	12.25%	14.53%	10.47%
Russell 2000® Value Index (reflects no deduction for fees, expenses or taxes)	7.84%	13.01%	8.17%

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Small Cap Value Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  SMALL CAP VALUE FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Small Cap Value Fund (the “Fund”) is to seek capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 59% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

59.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund is managed using a value oriented approach. The Sub-Adviser evaluates securities using fundamental analysis and intends to purchase equity investments that are, in its view, underpriced relative to a combination of such companies’ long term earnings prospects, growth rate, free cash flow and/or dividend-paying ability. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in a diversified portfolio of equity investments in small-cap issuers with public stock market capitalizations (measured at the time of purchase) within the range of the market capitalization of companies constituting the Russell 2000^® Value Index at the time of investment (as of March 31, 2018, this range was between $8 million and $8.44 billion). If the market capitalization of a company held by the Fund moves outside this range, the Fund may, but is not required to, sell the securities. Because the Fund’s definition of small-cap issuers is dynamic, the lower and upper limits on market capitalization will change with the markets. The Fund’s investments in small capitalization companies may include micro-capitalization companies and “unseasoned companies,” which are companies that (together with their predecessors) have operated for less than three years. The Russell 2000^® Value Index measures the performance of those Russell 2000 companies with lower price to book ratio and lower forecasted growth values. Through fundamental proprietary research the Fund will attempt to take advantage of what the Sub-Adviser believes to be well-positioned cash generating businesses run by shareholder-orientated managements. The Sub-Adviser will seek to buy these companies opportunistically at a price low enough to provide a healthy margin of safety. Under normal circumstances, the Fund’s investment horizons for ownership of stocks will be two to three years.

Although the Fund will invest primarily in publicly traded U.S. securities, including real estate investment trusts (“REITs”), it may invest up to 25% of its net assets in foreign securities, including securities of issuers in emerging countries and securities quoted in foreign currencies. The Fund may, but is not required to, undertake hedging activities and may invest in certain instruments, such as forward currency exchange contracts, and may use certain techniques to hedge currency risks associated with the purchase of individual securities denominated in a foreign currency. The Fund may invest in the aggregate up to 20% of its net assets in companies with public stock market capitalizations outside the range of companies constituting the Russell 2000^® Value Index at the time of investment and in fixed income securities, such as government, corporate, and bank debt obligations.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by the Fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

Interest Rate Risk.  The possibility that the prices of the Fund’s fixed income investments will decline due to rising interest rates.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Micro-Cap Securities Risk.  The possibility that the return on the Fund’s investments in micro-cap companies may be less than the return on investments in stocks of larger companies or the stock market as a whole. Stock prices of micro-cap companies may be based in substantial part on future expectations rather than current achievements and may move sharply, especially during market upturns and downturns. Micro-cap companies are followed by relatively few securities analysts, and there tends to be less publicly available information about these companies. Micro-cap companies are more likely to be newly formed or in the early stages of development, depend on a few key employees, and have relatively limited product lines, markets or financial resources compared to larger capitalization companies.

REITs Risk.  The possibility that the Fund’s investments in REITs will subject the Fund to the risks associated with the direct ownership of real estate, including fluctuations in the value of underlying properties, changes in interest rates and risks related to general or local economic conditions. REITs are dependent upon management skills and generally may not be diversified. REITs are also subject to heavy cash flow dependency, defaults by borrowers or tenants and self-liquidation.

Small- and Mid-Cap Securities Risk.  The possibility that the Fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and the Fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

Unseasoned Company Risk.  The possibility that the Fund’s investment in relatively new or unseasoned companies that are in their early stages of development may expose the Fund to greater risks than investments in more established companies with more extensive financial histories and greater liquidity. Unseasoned companies do not have proven track records and may lack substantial capital reserves.

“Value” Investing Risk.  The possibility that the Fund’s investments in securities believed by the Sub-Adviser to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which the Fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the Fund’s investment style shifts out of favor.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in small-cap stocks in the hope of earning above-average capital appreciation.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
19.74%	-25.20%
09/30/2009	12/31/2008

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Small Cap Value Fund | Small Cap Value Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.72%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.25%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.98%

^[1]

1 Year

rr_ExpenseExampleYear01

$ 100

3 Years

rr_ExpenseExampleYear03

312

5 Years

rr_ExpenseExampleYear05

542

10 Years

rr_ExpenseExampleYear10

$ 1,201

2008

rr_AnnualReturn2008

(27.15%)

2009

rr_AnnualReturn2009

26.93%

2010

rr_AnnualReturn2010

26.74%

2011

rr_AnnualReturn2011

0.87%

2012

rr_AnnualReturn2012

16.16%

2013

rr_AnnualReturn2013

38.93%

2014

rr_AnnualReturn2014

7.15%

2015

rr_AnnualReturn2015

(5.46%)

2016

rr_AnnualReturn2016

24.75%

2017

rr_AnnualReturn2017

12.25%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

19.74%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(25.20%)

1 Year

rr_AverageAnnualReturnYear01

12.25%

5 Years

rr_AverageAnnualReturnYear05

14.53%

10 Years

rr_AverageAnnualReturnYear10

10.47%

Penn Series Small Cap Value Fund | Russell 2000® Value Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

7.84%

5 Years

rr_AverageAnnualReturnYear05

13.01%

10 Years

rr_AverageAnnualReturnYear10

8.17%

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Penn Series Small Cap Index Fund

FUND SUMMARY:  SMALL CAP INDEX FUND

Investment Objective

The investment objective of the Small Cap Index Fund (the “Fund”) is to seek to replicate the returns and characteristics of a small cap index.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Small Cap Index Fund Small Cap Index Fund
Investment Advisory Fees	0.30%
Distribution (12b-1) Fees	none
Other Expenses	0.35%
Total Annual Fund Operating Expenses	0.65%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Small Cap Index Fund | Small Cap Index Fund | USD ($)	66	208	362	810

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 13% of the average value of its portfolio.

Principal Investment Strategy

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities listed in the Russell 2000^® Index (the "Index"). Under normal circumstances, however, the Fund intends to invest substantially all of its assets in securities of companies included in the Index and close substitutes (such as index futures contracts or other investment companies) that are designed to track the Index. The Index measures the performance of the 2,000 smallest companies (based on total market capitalization) in the Russell 3000^® Index. The Fund may concentrate (invest 25% or more of the value of its assets) in the securities of issuers having their principal business activities in the same industry if the Index is also concentrated in such industry. The Fund's investments in small capitalization companies may include micro-capitalization companies.

The Sub-Adviser does not manage the Fund according to traditional methods of "active" investment management, which involve the buying and selling of securities based upon economic, financial and market analysis and investment judgment. Instead, the Sub-Adviser utilizes a "passive" investment approach, attempting to replicate the investment performance of its benchmark Index through automated statistical analytic procedures.

The Sub-Adviser seeks to replicate the returns of the Index by investing in the securities of the Index in approximately their Index weight. However, under various circumstances, it may not be possible or practicable to purchase all of those securities in those weightings. In those circumstances, the Fund may purchase a sample of stocks in the Index in proportions expected to match generally the performance of the Index as a whole. In addition, from time to time, stocks are added to or removed from the Index. The Fund may sell stocks that are represented in the Index, or purchase stocks that are not yet represented in the Index, in anticipation of their removal from or addition to the Index.

The Sub-Adviser may at times purchase or sell futures contracts in lieu of investment directly in the stocks making up the Index. The Sub-Adviser might do so, for example, in order to increase the Fund's investment exposure pending investment of cash in the stocks comprising the Index. Alternatively, the Sub-Adviser might use futures to reduce its investment exposure to the Index in situations where it intends to sell a portion of the stocks in the Fund's portfolio but the sale has not yet been completed.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Concentration Risk.  The possibility that, to the extent the Fund invests to a significant extent in a particular industry or group of industries within a particular sector, the Fund may be subject to greater risks than if its investments were broadly diversified across industries and sectors. The Fund also is subject to loss due to adverse occurrences that may affect that industry or group of industries.

Counterparty Risk.  The possibility that a party to a transaction involving the Fund may fail to meet its obligations thereby causing the Fund to lose money or the benefit of the transaction or preventing the Fund from selling or buying other securities to implement its investment strategies.

Derivatives Risk.  The possibility that the Fund's use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Liquidity Risk.  The possibility that the market for certain of the Fund's investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Micro-Cap Securities Risk.  The possibility that the return on the Fund's investments in micro-cap companies may be less than the return on investments in stocks of larger companies or the stock market as a whole. Stock prices of micro-cap companies may be based in substantial part on future expectations rather than current achievements and may move sharply, especially during market upturns and downturns. Micro-cap companies are followed by relatively few securities analysts, and there tends to be less publicly available information about these companies. Micro-cap companies are more likely to be newly formed or in the early stages of development, depend on a few key employees, and have relatively limited product lines, markets or financial resources compared to larger capitalization companies.

Other Investment Company Risk.  The possibility that investments by the Fund in shares of other investment companies will subject the Fund to the risks associated with those investment companies. Fund shareholders will also indirectly bear a proportionate share of any underlying investment company's fees and expenses in addition to paying the Fund's expenses.

Passive Investment Risk.  The possibility that the Fund's return may be lower than the return of an actively managed fund because the Fund holds shares of a security based on the holdings of its benchmark index, not the current or projected performance of a security, industry or sector. The Fund does not take defensive positions under any market conditions, including declining markets.

Sampling Risk.  The possibility that the Fund may not hold all of the securities included in its benchmark index and that the securities selected for the Fund, in the aggregate, will not provide investment performance matching that of the Fund's benchmark index.

Small-Cap Securities Risk.  The possibility that the return on the Fund's investments in small-cap companies may trail the return on investments in stocks of larger companies or the stock market as a whole. Stock prices of smaller companies may be based in substantial part on future expectations rather than current achievements and may move sharply, especially during market upturns and downturns. Small-cap companies generally depend on a few key employees and have relatively limited product lines, markets or financial resources compared to larger capitalization companies.

Tracking Error Risk.  The possibility that the Sub-Adviser may not be able to cause the Fund's performance to correspond to that of the Index, either on a daily or aggregate basis. Factors such as Fund expenses, imperfect correlation between the Fund's investments and those of the Index, rounding of share prices, changes to the composition of the Index, regulatory policies, and high portfolio turnover rate all contribute to tracking error. Tracking error may cause the Fund's performance to be less than you expect.

Unconstrained Sector Risk.  The possibility that the Fund may invest a substantial portion of its assets within one or more economic sectors or industries, which may change from time to time. Greater investment focus on one or more sectors or industries increases the potential for volatility and the risk that events negatively affecting such sectors or industries could reduce returns, potentially causing the value of the Fund's shares to decrease, perhaps significantly.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in small cap common stocks in the hope of achieving returns similar to that of the Index.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
20.47%	-21.94%
6/30/2009	9/30/2011

Average Annual Total Return (for Periods Ended December 31, 2017

Average Annual Total Returns - Penn Series Small Cap Index Fund	1 Year	5 Years	Since Inception	Inception Date
Small Cap Index Fund	13.79%	13.34%	9.32%	Aug. 25, 2008
Russell 2000® Index (reflects no deduction for fees, expenses or taxes)	14.65%	14.12%	9.69%	Aug. 25, 2008

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Small Cap Index Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  SMALL CAP INDEX FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Small Cap Index Fund (the “Fund”) is to seek to replicate the returns and characteristics of a small cap index.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 13% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

13.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities listed in the Russell 2000^® Index (the "Index"). Under normal circumstances, however, the Fund intends to invest substantially all of its assets in securities of companies included in the Index and close substitutes (such as index futures contracts or other investment companies) that are designed to track the Index. The Index measures the performance of the 2,000 smallest companies (based on total market capitalization) in the Russell 3000^® Index. The Fund may concentrate (invest 25% or more of the value of its assets) in the securities of issuers having their principal business activities in the same industry if the Index is also concentrated in such industry. The Fund's investments in small capitalization companies may include micro-capitalization companies.

The Sub-Adviser does not manage the Fund according to traditional methods of "active" investment management, which involve the buying and selling of securities based upon economic, financial and market analysis and investment judgment. Instead, the Sub-Adviser utilizes a "passive" investment approach, attempting to replicate the investment performance of its benchmark Index through automated statistical analytic procedures.

The Sub-Adviser seeks to replicate the returns of the Index by investing in the securities of the Index in approximately their Index weight. However, under various circumstances, it may not be possible or practicable to purchase all of those securities in those weightings. In those circumstances, the Fund may purchase a sample of stocks in the Index in proportions expected to match generally the performance of the Index as a whole. In addition, from time to time, stocks are added to or removed from the Index. The Fund may sell stocks that are represented in the Index, or purchase stocks that are not yet represented in the Index, in anticipation of their removal from or addition to the Index.

The Sub-Adviser may at times purchase or sell futures contracts in lieu of investment directly in the stocks making up the Index. The Sub-Adviser might do so, for example, in order to increase the Fund's investment exposure pending investment of cash in the stocks comprising the Index. Alternatively, the Sub-Adviser might use futures to reduce its investment exposure to the Index in situations where it intends to sell a portion of the stocks in the Fund's portfolio but the sale has not yet been completed.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund may concentrate (invest 25% or more of the value of its assets) in the securities of issuers having their principal business activities in the same industry if the Index is also concentrated in such industry.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Concentration Risk.  The possibility that, to the extent the Fund invests to a significant extent in a particular industry or group of industries within a particular sector, the Fund may be subject to greater risks than if its investments were broadly diversified across industries and sectors. The Fund also is subject to loss due to adverse occurrences that may affect that industry or group of industries.

Counterparty Risk.  The possibility that a party to a transaction involving the Fund may fail to meet its obligations thereby causing the Fund to lose money or the benefit of the transaction or preventing the Fund from selling or buying other securities to implement its investment strategies.

Derivatives Risk.  The possibility that the Fund's use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Liquidity Risk.  The possibility that the market for certain of the Fund's investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Micro-Cap Securities Risk.  The possibility that the return on the Fund's investments in micro-cap companies may be less than the return on investments in stocks of larger companies or the stock market as a whole. Stock prices of micro-cap companies may be based in substantial part on future expectations rather than current achievements and may move sharply, especially during market upturns and downturns. Micro-cap companies are followed by relatively few securities analysts, and there tends to be less publicly available information about these companies. Micro-cap companies are more likely to be newly formed or in the early stages of development, depend on a few key employees, and have relatively limited product lines, markets or financial resources compared to larger capitalization companies.

Other Investment Company Risk.  The possibility that investments by the Fund in shares of other investment companies will subject the Fund to the risks associated with those investment companies. Fund shareholders will also indirectly bear a proportionate share of any underlying investment company's fees and expenses in addition to paying the Fund's expenses.

Passive Investment Risk.  The possibility that the Fund's return may be lower than the return of an actively managed fund because the Fund holds shares of a security based on the holdings of its benchmark index, not the current or projected performance of a security, industry or sector. The Fund does not take defensive positions under any market conditions, including declining markets.

Sampling Risk.  The possibility that the Fund may not hold all of the securities included in its benchmark index and that the securities selected for the Fund, in the aggregate, will not provide investment performance matching that of the Fund's benchmark index.

Small-Cap Securities Risk.  The possibility that the return on the Fund's investments in small-cap companies may trail the return on investments in stocks of larger companies or the stock market as a whole. Stock prices of smaller companies may be based in substantial part on future expectations rather than current achievements and may move sharply, especially during market upturns and downturns. Small-cap companies generally depend on a few key employees and have relatively limited product lines, markets or financial resources compared to larger capitalization companies.

Tracking Error Risk.  The possibility that the Sub-Adviser may not be able to cause the Fund's performance to correspond to that of the Index, either on a daily or aggregate basis. Factors such as Fund expenses, imperfect correlation between the Fund's investments and those of the Index, rounding of share prices, changes to the composition of the Index, regulatory policies, and high portfolio turnover rate all contribute to tracking error. Tracking error may cause the Fund's performance to be less than you expect.

Unconstrained Sector Risk.  The possibility that the Fund may invest a substantial portion of its assets within one or more economic sectors or industries, which may change from time to time. Greater investment focus on one or more sectors or industries increases the potential for volatility and the risk that events negatively affecting such sectors or industries could reduce returns, potentially causing the value of the Fund's shares to decrease, perhaps significantly.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in small cap common stocks in the hope of achieving returns similar to that of the Index.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
20.47%	-21.94%
6/30/2009	9/30/2011

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017

Penn Series Small Cap Index Fund | Small Cap Index Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.30%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.35%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.65%

1 Year

rr_ExpenseExampleYear01

$ 66

3 Years

rr_ExpenseExampleYear03

208

5 Years

rr_ExpenseExampleYear05

362

10 Years

rr_ExpenseExampleYear10

$ 810

2009

rr_AnnualReturn2009

26.15%

2010

rr_AnnualReturn2010

26.20%

2011

rr_AnnualReturn2011

(4.51%)

2012

rr_AnnualReturn2012

15.50%

2013

rr_AnnualReturn2013

38.13%

2014

rr_AnnualReturn2014

4.21%

2015

rr_AnnualReturn2015

(5.12%)

2016

rr_AnnualReturn2016

20.37%

2017

rr_AnnualReturn2017

13.79%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

20.47%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(21.94%)

1 Year

rr_AverageAnnualReturnYear01

13.79%

5 Years

rr_AverageAnnualReturnYear05

13.34%

Since Inception

rr_AverageAnnualReturnSinceInception

9.32%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Small Cap Index Fund | Russell 2000® Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

14.65%

5 Years

rr_AverageAnnualReturnYear05

14.12%

Since Inception

rr_AverageAnnualReturnSinceInception

9.69%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

XML

Penn Series Developed International Index Fund

FUND SUMMARY:  DEVELOPED INTERNATIONAL INDEX FUND

Investment Objective

The investment objective of the Developed International Index Fund (the “Fund”) is to seek to replicate the returns and characteristics of an international index composed of securities from developed countries.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Developed International Index Fund Developed International Index Fund
Investment Advisory Fees	0.30%
Distribution (12b-1) Fees	none
Other Expenses	0.52%
Total Annual Fund Operating Expenses	0.82%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Developed International Index Fund | Developed International Index Fund | USD ($)	84	262	455	1,014

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 4% of the average value of its portfolio.

Principal Investment Strategy

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities listed in the MSCI^® Europe, Australasia, Far East (MSCI EAFE) Index (the “Index”). Under normal circumstances, however, the Fund intends to invest substantially all of its assets in securities of companies included in the Index (including ADRs and Global Depositary Receipts (“GDRs”)) and close substitutes (such as index futures contracts) that are designed to track the Index. The Index is an arithmetic, market value-weighted average of the performance of approximately 1,000 securities primarily from Europe, Australia, Asia and the Far East. The Fund may concentrate (invest 25% or more of the value of its assets) in the securities of issuers having their principal business activities in the same industry if the Index is also concentrated in such industry.

The Sub-Adviser does not manage the Fund according to traditional methods of “active” investment management, which involve the buying and selling of securities based upon economic, financial and market analysis and investment judgment. Instead, the Sub-Adviser utilizes a “passive” investment approach, attempting to replicate the investment performance of its benchmark Index through automated statistical analytic procedures.

The Sub-Adviser seeks to replicate the returns of the Index by investing in the securities of the Index in approximately their Index weight. However, under various circumstances, it may not be possible or practicable to purchase all of those securities in those weightings. In those circumstances, the Fund may purchase a sample of stocks in the Index in proportions expected to match generally the performance of the Index as a whole. In addition, from time to time, stocks are added to or removed from the Index. The Fund may sell stocks that are represented in the Index, or purchase stocks that are not yet represented in the Index, in anticipation of their removal from or addition to the Index.

The Sub-Adviser may at times purchase or sell futures contracts in lieu of investment directly in the stocks making up the Index. The Sub-Adviser might do so, for example, in order to increase the Fund’s investment exposure pending investment of cash in the stocks comprising the Index. Alternatively, the Sub-Adviser might use futures to reduce its investment exposure to the Index in situations where it intends to sell a portion of the stocks in the Fund’s portfolio but the sale has not yet been completed. The Sub-Adviser may also enter into forward foreign currency exchange contracts in an attempt to match the Index’s currency exposures.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Concentration Risk.  The possibility that, to the extent the Fund invests to a significant extent in a particular industry or group of industries within a particular sector, the Fund may be subject to greater risks than if its investments were broadly diversified across industries and sectors. The Fund also is subject to loss due to adverse occurrences that may affect that industry or group of industries.

Counterparty Risk.  The possibility that a party to a transaction involving the Fund may fail to meet its obligations thereby causing the Fund to lose money or the benefit of the transaction or preventing the Fund from selling or buying other securities to implement its investment strategies.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Depositary Receipt Risk.  The possibility that the Fund’s investments in foreign companies through depositary receipts will expose the Fund to the same risks as direct investment in securities of foreign issuers. In addition, investments in ADRs and GDRs may be less liquid than the underlying shares in their primary trading market, and the value of securities underlying ADRs and GDRs may change materially at times when U.S. markets are not open for trading.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

Geographic Focus Risk.  The possibility that the Fund may be less diversified across countries or geographic regions and the Fund’s performance will be closely tied to market, currency, economic, political, environmental, or regulatory conditions and developments in the countries or regions in which the Fund invests, and may be more volatile than the performance of a more geographically-diversified fund.

Europe.  Developed and emerging market countries in Europe will be significantly affected by the fiscal and monetary controls of the Economic and Monetary Union of the European Union (“EU”). Changes in regulations on trade, decreasing imports or exports, changes in the exchange rate of the euro and recessions among European countries may have a significant adverse effect on the economies of other European countries. In addition, one or more countries may abandon the euro and/or withdraw from the EU. For example, in June 2016, citizens of the United Kingdom voted in a referendum to leave the EU (known as “Brexit”), creating economic and political uncertainty in its wake. In March 2017, the United Kingdom formally notified the European Council of the United Kingdom’s intention to withdraw from the EU pursuant to Article 50 of the Treaty on European Union. This formal notification began a two-year period of negotiations regarding the terms of the United Kingdom’s exit from the EU. It is unclear how withdrawal negotiations will be conducted and what the potential consequences may be. Any exits from the EU, or the possibility of such exits, may have a significant impact on the United Kingdom, Europe, and global economies, which may result in increased volatility and illiquidity, new legal and regulatory uncertainties and potentially lower economic growth for such economies that could potentially have an adverse effect on the value of the Fund’s investments. In addition, a number of countries in Europe have suffered terrorist attacks and additional attacks may occur in the future. Such attacks may cause uncertainty in financial markets and may adversely affect the performance of the issuers to which the Fund has exposure.

Japan.  The growth of Japan’s economy has historically lagged that of its Asian neighbors and other major developed economies. The Japanese economy is heavily dependent on international trade and has been adversely affected by trade tariffs, other protectionist measures, competition from emerging economies and the economic conditions of its trading partners. China has become an important trading partner with Japan, yet the countries’ political relationship has become strained. Should political tension increase, it could adversely affect the economy, especially the export sector, and destabilize the region as a whole. Japan also remains heavily dependent on oil imports, and higher commodity prices could therefore have a negative impact on the economy. The Japanese yen has fluctuated widely at times and any increase in its value may cause a decline in exports that could weaken the Japanese economy. Japan has, in the past, intervened in the currency markets to attempt to maintain or reduce the value of the yen. Japanese intervention in the currency markets could cause the value of the yen to fluctuate sharply and unpredictably and could cause losses to investors. Japan has an aging workforce and has experienced a significant population decline in recent years. Japan’s labor market appears to be undergoing fundamental structural changes, as a labor market traditionally accustomed to lifetime employment adjusts to meet the need for increased labor mobility, which may adversely affect Japan’s economic competitiveness. Natural disasters, such as earthquakes, volcanoes, typhoons or tsunamis, could occur in Japan or surrounding areas and could negatively affect the Japanese economy and, in turn, the Fund.

United Kingdom.  The United Kingdom has one of the largest economies in Europe, and the United States and other European countries are substantial trading partners of the United Kingdom. As a result, the British economy may be impacted by changes to the economic condition of the United States and other European countries. The British economy, along with certain other EU economies, experienced a significant economic slowdown during the recent financial crisis, and certain British financial institutions suffered significant losses, were severely under-capitalized and required government intervention to survive. The British economy relies heavily on the export of financial services to the United States and other European countries and, therefore, a prolonged slowdown in the financial services sector may have a negative impact on the British economy. Continued governmental involvement or control in certain sectors may stifle competition in certain sectors or cause adverse effects on economic growth. In June 2016, the United Kingdom voted in a referendum to leave the EU. For more information about “Brexit” and the associated risks, see the above description of risks related to investments in Europe.

Large-Cap Securities Risk.  The possibility that the Fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Mid-Cap Securities Risk.  The possibility that the return on the Fund’s investments in mid-cap companies may be less than the return on investments in stocks of larger or smaller companies or the stock market as a whole. Mid-cap companies may be more vulnerable to market volatility and adverse business or economic events than larger, more established companies. The securities of mid-cap companies are more likely to trade in lower volumes and are generally subject to greater and less predictable price changes than the securities of larger capitalization companies.

Passive Investment Risk.  The possibility that the Fund’s return may be lower than the return of an actively managed fund because the Fund holds shares of a security based on the holdings of its benchmark index, not the current or projected performance of a security, industry or sector. The Fund does not take defensive positions under any market conditions, including declining markets.

Sampling Risk.  The possibility that the Fund may not hold all of the securities included in its benchmark index and that the securities selected for the Fund, in the aggregate, will not provide investment performance matching that of the Fund’s benchmark index.

Tracking Error Risk.  The possibility that the Sub-Adviser may not be able to cause the Fund’s performance to correspond to that of the Index, either on a daily or aggregate basis. Factors such as Fund expenses, imperfect correlation between the Fund’s investments and those of the Index, rounding of share prices, changes to the composition of the Index, regulatory policies, and high portfolio turnover rate all contribute to tracking error. Tracking error may cause the Fund’s performance to be less than you expect.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in international securities in the hope of achieving returns similar to that of the Index.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
25.12%	-20.12%
6/30/2009	9/30/2011

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Developed International Index Fund	1 Year	5 Years	Since Inception	Inception Date
Developed International Index Fund	24.52%	6.98%	3.88%	Aug. 25, 2008
MSCI EAFE Index (Index returns do not reflect deductions for fees, expenses or taxes, including taxes on foreign dividends)	25.62%	8.39%	4.86%	Aug. 25, 2008

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Developed International Index Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  DEVELOPED INTERNATIONAL INDEX FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Developed International Index Fund (the “Fund”) is to seek to replicate the returns and characteristics of an international index composed of securities from developed countries.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 4% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

4.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities listed in the MSCI^® Europe, Australasia, Far East (MSCI EAFE) Index (the “Index”). Under normal circumstances, however, the Fund intends to invest substantially all of its assets in securities of companies included in the Index (including ADRs and Global Depositary Receipts (“GDRs”)) and close substitutes (such as index futures contracts) that are designed to track the Index. The Index is an arithmetic, market value-weighted average of the performance of approximately 1,000 securities primarily from Europe, Australia, Asia and the Far East. The Fund may concentrate (invest 25% or more of the value of its assets) in the securities of issuers having their principal business activities in the same industry if the Index is also concentrated in such industry.

The Sub-Adviser does not manage the Fund according to traditional methods of “active” investment management, which involve the buying and selling of securities based upon economic, financial and market analysis and investment judgment. Instead, the Sub-Adviser utilizes a “passive” investment approach, attempting to replicate the investment performance of its benchmark Index through automated statistical analytic procedures.

The Sub-Adviser seeks to replicate the returns of the Index by investing in the securities of the Index in approximately their Index weight. However, under various circumstances, it may not be possible or practicable to purchase all of those securities in those weightings. In those circumstances, the Fund may purchase a sample of stocks in the Index in proportions expected to match generally the performance of the Index as a whole. In addition, from time to time, stocks are added to or removed from the Index. The Fund may sell stocks that are represented in the Index, or purchase stocks that are not yet represented in the Index, in anticipation of their removal from or addition to the Index.

The Sub-Adviser may at times purchase or sell futures contracts in lieu of investment directly in the stocks making up the Index. The Sub-Adviser might do so, for example, in order to increase the Fund’s investment exposure pending investment of cash in the stocks comprising the Index. Alternatively, the Sub-Adviser might use futures to reduce its investment exposure to the Index in situations where it intends to sell a portion of the stocks in the Fund’s portfolio but the sale has not yet been completed. The Sub-Adviser may also enter into forward foreign currency exchange contracts in an attempt to match the Index’s currency exposures.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund may concentrate (invest 25% or more of the value of its assets) in the securities of issuers having their principal business activities in the same industry if the Index is also concentrated in such industry.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Concentration Risk.  The possibility that, to the extent the Fund invests to a significant extent in a particular industry or group of industries within a particular sector, the Fund may be subject to greater risks than if its investments were broadly diversified across industries and sectors. The Fund also is subject to loss due to adverse occurrences that may affect that industry or group of industries.

Counterparty Risk.  The possibility that a party to a transaction involving the Fund may fail to meet its obligations thereby causing the Fund to lose money or the benefit of the transaction or preventing the Fund from selling or buying other securities to implement its investment strategies.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Depositary Receipt Risk.  The possibility that the Fund’s investments in foreign companies through depositary receipts will expose the Fund to the same risks as direct investment in securities of foreign issuers. In addition, investments in ADRs and GDRs may be less liquid than the underlying shares in their primary trading market, and the value of securities underlying ADRs and GDRs may change materially at times when U.S. markets are not open for trading.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

Geographic Focus Risk.  The possibility that the Fund may be less diversified across countries or geographic regions and the Fund’s performance will be closely tied to market, currency, economic, political, environmental, or regulatory conditions and developments in the countries or regions in which the Fund invests, and may be more volatile than the performance of a more geographically-diversified fund.

Europe.  Developed and emerging market countries in Europe will be significantly affected by the fiscal and monetary controls of the Economic and Monetary Union of the European Union (“EU”). Changes in regulations on trade, decreasing imports or exports, changes in the exchange rate of the euro and recessions among European countries may have a significant adverse effect on the economies of other European countries. In addition, one or more countries may abandon the euro and/or withdraw from the EU. For example, in June 2016, citizens of the United Kingdom voted in a referendum to leave the EU (known as “Brexit”), creating economic and political uncertainty in its wake. In March 2017, the United Kingdom formally notified the European Council of the United Kingdom’s intention to withdraw from the EU pursuant to Article 50 of the Treaty on European Union. This formal notification began a two-year period of negotiations regarding the terms of the United Kingdom’s exit from the EU. It is unclear how withdrawal negotiations will be conducted and what the potential consequences may be. Any exits from the EU, or the possibility of such exits, may have a significant impact on the United Kingdom, Europe, and global economies, which may result in increased volatility and illiquidity, new legal and regulatory uncertainties and potentially lower economic growth for such economies that could potentially have an adverse effect on the value of the Fund’s investments. In addition, a number of countries in Europe have suffered terrorist attacks and additional attacks may occur in the future. Such attacks may cause uncertainty in financial markets and may adversely affect the performance of the issuers to which the Fund has exposure.

Japan.  The growth of Japan’s economy has historically lagged that of its Asian neighbors and other major developed economies. The Japanese economy is heavily dependent on international trade and has been adversely affected by trade tariffs, other protectionist measures, competition from emerging economies and the economic conditions of its trading partners. China has become an important trading partner with Japan, yet the countries’ political relationship has become strained. Should political tension increase, it could adversely affect the economy, especially the export sector, and destabilize the region as a whole. Japan also remains heavily dependent on oil imports, and higher commodity prices could therefore have a negative impact on the economy. The Japanese yen has fluctuated widely at times and any increase in its value may cause a decline in exports that could weaken the Japanese economy. Japan has, in the past, intervened in the currency markets to attempt to maintain or reduce the value of the yen. Japanese intervention in the currency markets could cause the value of the yen to fluctuate sharply and unpredictably and could cause losses to investors. Japan has an aging workforce and has experienced a significant population decline in recent years. Japan’s labor market appears to be undergoing fundamental structural changes, as a labor market traditionally accustomed to lifetime employment adjusts to meet the need for increased labor mobility, which may adversely affect Japan’s economic competitiveness. Natural disasters, such as earthquakes, volcanoes, typhoons or tsunamis, could occur in Japan or surrounding areas and could negatively affect the Japanese economy and, in turn, the Fund.

United Kingdom.  The United Kingdom has one of the largest economies in Europe, and the United States and other European countries are substantial trading partners of the United Kingdom. As a result, the British economy may be impacted by changes to the economic condition of the United States and other European countries. The British economy, along with certain other EU economies, experienced a significant economic slowdown during the recent financial crisis, and certain British financial institutions suffered significant losses, were severely under-capitalized and required government intervention to survive. The British economy relies heavily on the export of financial services to the United States and other European countries and, therefore, a prolonged slowdown in the financial services sector may have a negative impact on the British economy. Continued governmental involvement or control in certain sectors may stifle competition in certain sectors or cause adverse effects on economic growth. In June 2016, the United Kingdom voted in a referendum to leave the EU. For more information about “Brexit” and the associated risks, see the above description of risks related to investments in Europe.

Large-Cap Securities Risk.  The possibility that the Fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Mid-Cap Securities Risk.  The possibility that the return on the Fund’s investments in mid-cap companies may be less than the return on investments in stocks of larger or smaller companies or the stock market as a whole. Mid-cap companies may be more vulnerable to market volatility and adverse business or economic events than larger, more established companies. The securities of mid-cap companies are more likely to trade in lower volumes and are generally subject to greater and less predictable price changes than the securities of larger capitalization companies.

Passive Investment Risk.  The possibility that the Fund’s return may be lower than the return of an actively managed fund because the Fund holds shares of a security based on the holdings of its benchmark index, not the current or projected performance of a security, industry or sector. The Fund does not take defensive positions under any market conditions, including declining markets.

Sampling Risk.  The possibility that the Fund may not hold all of the securities included in its benchmark index and that the securities selected for the Fund, in the aggregate, will not provide investment performance matching that of the Fund’s benchmark index.

Tracking Error Risk.  The possibility that the Sub-Adviser may not be able to cause the Fund’s performance to correspond to that of the Index, either on a daily or aggregate basis. Factors such as Fund expenses, imperfect correlation between the Fund’s investments and those of the Index, rounding of share prices, changes to the composition of the Index, regulatory policies, and high portfolio turnover rate all contribute to tracking error. Tracking error may cause the Fund’s performance to be less than you expect.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in international securities in the hope of achieving returns similar to that of the Index.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
25.12%	-20.12%
6/30/2009	9/30/2011

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Developed International Index Fund | Developed International Index Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.30%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.52%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.82%

1 Year

rr_ExpenseExampleYear01

$ 84

3 Years

rr_ExpenseExampleYear03

262

5 Years

rr_ExpenseExampleYear05

455

10 Years

rr_ExpenseExampleYear10

$ 1,014

2009

rr_AnnualReturn2009

28.52%

2010

rr_AnnualReturn2010

7.43%

2011

rr_AnnualReturn2011

(12.61%)

2012

rr_AnnualReturn2012

18.16%

2013

rr_AnnualReturn2013

21.08%

2014

rr_AnnualReturn2014

(6.10%)

2015

rr_AnnualReturn2015

(1.39%)

2016

rr_AnnualReturn2016

0.35%

2017

rr_AnnualReturn2017

24.52%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

25.12%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(20.12%)

1 Year

rr_AverageAnnualReturnYear01

24.52%

5 Years

rr_AverageAnnualReturnYear05

6.98%

Since Inception

rr_AverageAnnualReturnSinceInception

3.88%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Developed International Index Fund | MSCI EAFE Index (Index returns do not reflect deductions for fees, expenses or taxes, including taxes on foreign dividends)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

25.62%

5 Years

rr_AverageAnnualReturnYear05

8.39%

Since Inception

rr_AverageAnnualReturnSinceInception

4.86%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

XML

Penn Series International Equity Fund

FUND SUMMARY:  INTERNATIONAL EQUITY FUND

Investment Objective

The investment objective of the International Equity Fund (the “Fund”) is to achieve capital appreciation.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series International Equity Fund International Equity Fund
Investment Advisory Fees	0.85%
Distribution (12b-1) Fees	none
Other Expenses	0.27%
Total Annual Fund Operating Expenses	1.12%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series International Equity Fund | International Equity Fund | USD ($)	114	356	617	1,363

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 32% of the average value of its portfolio.

Principal Investment Strategy

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities, such as common stocks, preferred stocks, convertible bonds, and warrants. The Fund will invest primarily in companies operating in the countries in Europe and the Pacific Basin. The countries include the eleven Euro-zone countries (France, Germany, Italy, Spain, Portugal, Finland, Ireland, Belgium, the Netherlands, Luxembourg and Austria), the United Kingdom, Denmark, Sweden, Switzerland, Norway, Japan, Hong Kong, Australia, New Zealand, and Singapore. The Sub-Adviser employs bottom-up stock and business analysis to identify high-quality growth companies. Typically, these companies tend to be well managed with the following attributes: consistent operating histories and financial performance; favorable long-term economic prospects; free cash flow generation; and competent management that can be counted on to use cash flow wisely, and channel the reward from the business back to its shareholders. The Sub-Adviser’s goal is to construct a portfolio of high-quality growth companies in the developed markets of Europe and the Pacific Basin. With approximately 40-70 stocks, the Fund seeks to be well diversified and will have investments in at least 10 countries and 5 sectors at all times. The Fund may invest in securities of companies in emerging and developing markets. The Fund may, but is not required to, undertake hedging activities and may invest in certain instruments, such as forward currency exchange contracts, and may use certain techniques to hedge currency risks associated with the purchase of individual securities denominated in a foreign currency.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Convertible Securities Risk.  The possibility that the value of the Fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Preferred Stock Risk.  The possibility that the value of the Fund’s investments in preferred stock may decline if stock prices fall or interest rates rise. In the event of a liquidation, the rights of a company’s preferred stock to the distribution of company assets are generally subordinate to the rights of a company’s debt securities.

Warrants Risk.  The possibility that the Fund’s investments in warrants are subject to greater price volatility than the warrants’ underlying securities. Warrants offer greater potential for profit or loss than an equivalent investment in the underlying security. A warrant generally ceases to have value if it is not exercised prior to its expiration date.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of international investing in the hope of realizing capital appreciation while diversifying their investment portfolio.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
18.48%	-19.10%
6/30/2009	9/30/2008

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series International Equity Fund	1 Year	5 Years	10 Years
International Equity Fund	31.68%	7.13%	3.19%
MSCI ACWI ex-U.S. Index (Index returns do not reflect deductions for fees, expenses or taxes, including taxes on foreign dividends)	27.77%	7.28%	2.31%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series International Equity Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  INTERNATIONAL EQUITY FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the International Equity Fund (the “Fund”) is to achieve capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 32% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

32.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities, such as common stocks, preferred stocks, convertible bonds, and warrants. The Fund will invest primarily in companies operating in the countries in Europe and the Pacific Basin. The countries include the eleven Euro-zone countries (France, Germany, Italy, Spain, Portugal, Finland, Ireland, Belgium, the Netherlands, Luxembourg and Austria), the United Kingdom, Denmark, Sweden, Switzerland, Norway, Japan, Hong Kong, Australia, New Zealand, and Singapore. The Sub-Adviser employs bottom-up stock and business analysis to identify high-quality growth companies. Typically, these companies tend to be well managed with the following attributes: consistent operating histories and financial performance; favorable long-term economic prospects; free cash flow generation; and competent management that can be counted on to use cash flow wisely, and channel the reward from the business back to its shareholders. The Sub-Adviser’s goal is to construct a portfolio of high-quality growth companies in the developed markets of Europe and the Pacific Basin. With approximately 40-70 stocks, the Fund seeks to be well diversified and will have investments in at least 10 countries and 5 sectors at all times. The Fund may invest in securities of companies in emerging and developing markets. The Fund may, but is not required to, undertake hedging activities and may invest in certain instruments, such as forward currency exchange contracts, and may use certain techniques to hedge currency risks associated with the purchase of individual securities denominated in a foreign currency.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Convertible Securities Risk.  The possibility that the value of the Fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Preferred Stock Risk.  The possibility that the value of the Fund’s investments in preferred stock may decline if stock prices fall or interest rates rise. In the event of a liquidation, the rights of a company’s preferred stock to the distribution of company assets are generally subordinate to the rights of a company’s debt securities.

Warrants Risk.  The possibility that the Fund’s investments in warrants are subject to greater price volatility than the warrants’ underlying securities. Warrants offer greater potential for profit or loss than an equivalent investment in the underlying security. A warrant generally ceases to have value if it is not exercised prior to its expiration date.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of international investing in the hope of realizing capital appreciation while diversifying their investment portfolio.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
18.48%	-19.10%
6/30/2009	9/30/2008

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series International Equity Fund | International Equity Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.85%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.27%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.12%

1 Year

rr_ExpenseExampleYear01

$ 114

3 Years

rr_ExpenseExampleYear03

356

5 Years

rr_ExpenseExampleYear05

617

10 Years

rr_ExpenseExampleYear10

$ 1,363

2008

rr_AnnualReturn2008

(41.28%)

2009

rr_AnnualReturn2009

21.74%

2010

rr_AnnualReturn2010

11.08%

2011

rr_AnnualReturn2011

0.91%

2012

rr_AnnualReturn2012

21.06%

2013

rr_AnnualReturn2013

5.97%

2014

rr_AnnualReturn2014

2.95%

2015

rr_AnnualReturn2015

3.59%

2016

rr_AnnualReturn2016

(5.16%)

2017

rr_AnnualReturn2017

31.68%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

18.48%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(19.10%)

1 Year

rr_AverageAnnualReturnYear01

31.68%

5 Years

rr_AverageAnnualReturnYear05

7.13%

10 Years

rr_AverageAnnualReturnYear10

3.19%

Penn Series International Equity Fund | MSCI ACWI ex-U.S. Index (Index returns do not reflect deductions for fees, expenses or taxes, including taxes on foreign dividends)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

27.77%

5 Years

rr_AverageAnnualReturnYear05

7.28%

10 Years

rr_AverageAnnualReturnYear10

2.31%

XML

Penn Series Emerging Markets Equity Fund

FUND SUMMARY:  EMERGING MARKETS EQUITY FUND

Investment Objective

The investment objective of the Emerging Markets Equity Fund (the “Fund”) is to seek to achieve capital appreciation.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Emerging Markets Equity Fund Emerging Markets Equity Fund
Investment Advisory Fees	0.92%
Distribution (12b-1) Fees	none
Other Expenses	0.49%
Total Annual Fund Operating Expenses	1.41%	[1]

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Emerging Markets Equity Fund | Emerging Markets Equity Fund | USD ($)	144	446	771	1,691

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 41% of the average value of its portfolio.

Principal Investment Strategy

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities located in emerging market countries. For this Fund, an issuer is considered to be located in an emerging market country if, at the time of investment: (i) its principal securities trading market is in an emerging market country, (ii) alone or on a consolidated basis it derives 50% or more of its annual revenue or profits from goods produced, sales made or services performed in emerging market countries or it has at least 50% of its assets in emerging markets countries, or (iii) it is organized under the laws of, or has a principal office in, an emerging market country. By applying this test, it is possible that a particular issuer could be deemed to be from more than one emerging market country.

The Sub-Adviser considers emerging market countries to be countries that major international financial institutions, such as the World Bank, or the Fund’s benchmark index generally consider to be less economically mature than developed nations, such as the United States or most nations in Western Europe. Emerging market countries can include every nation in the world except the United States, Canada, Japan, Australia, New Zealand and most nations located in Western Europe. Allocation of the Fund’s investments will depend upon the relative attractiveness of emerging countries and particular issuers. There are no prescribed limits on the geographic distribution of the Fund’s investments.

The investment process takes into account information about environmental, social and governance issues (also referred to as ESG) when making investment decisions. The Sub-Adviser focuses on engaging company management around corporate governance practices as well as what the Sub-Adviser deems to be materially important environmental and/or social issues facing a company.

The Sub-Adviser seeks to maximize returns by investing in growth-oriented equity securities of emerging country issuers. The Sub-Adviser combines top-down country criteria to allocate the Fund’s assets among countries (based on relative economic, political and social fundamentals, stock valuations, and investor sentiment) with bottom-up fundamental analysis of issuers (seeking to identify issuers with strong earnings growth potential). The Sub-Adviser attempts to manage the overall risk of its investments through its emphasis on thorough macroeconomic and fundamental research.

The Fund invests primarily in equity securities, including common stocks and convertible securities. The Fund may invest in securities of micro-, small-, medium- and large-capitalization companies. The Fund may invest in derivative instruments, including futures, options, swaps and forward foreign currency exchange contracts. The Fund may, but is not required to, use these derivative instruments for a variety of purposes, including hedging, risk management, portfolio management and to earn income. Derivative instruments used by the Fund will be counted toward the Fund’s 80% policy discussed above to the extent they have economic characteristics similar to the securities included within that policy.

The Fund may buy and sell portfolio securities actively. If it does, its portfolio turnover rate and transaction costs will rise, which may lower Fund performance.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Convertible Securities Risk.  The possibility that the value of the Fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Credit Risk.  The possibility that the counterparty to a derivatives contract held by the Fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options, swap agreements and forward foreign currency exchange contracts, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that the Fund’s investments in securities of companies perceived to be “growth” companies may underperform when the Fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

Interest Rate Risk.  The possibility that the prices of the Fund’s convertible securities will decline due to rising interest rates.

Large-Cap Securities Risk.  The possibility that the Fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Micro-Cap Securities Risk.  The possibility that the return on the Fund’s investments in micro-cap companies may be less than the return on investments in stocks of larger companies or the stock market as a whole. Stock prices of micro-cap companies may be based in substantial part on future expectations rather than current achievements and may move sharply, especially during market upturns and downturns. Micro-cap companies are followed by relatively few securities analysts, and there tends to be less publicly available information about these companies. Micro-cap companies are more likely to be newly formed or in the early stages of development, depend on a few key employees, and have relatively limited product lines, markets or financial resources compared to larger capitalization companies.

Portfolio Turnover Risk.  The possibility that the Fund may frequently buy and sell portfolio securities, which may increase transaction costs to the Fund and cause the Fund’s performance to be less than you expect.

Small- and Mid-Cap Securities Risk.  The possibility that the Fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and the Fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in emerging market equity securities in the hope of achieving capital appreciation.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
34.74%	-19.38%
6/30/2009	9/30/2011

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Emerging Markets Equity Fund	1 Year	5 Years	Since Inception	Inception Date
Emerging Markets Equity Fund	35.03%	3.66%	3.55%	Aug. 25, 2008
MSCI Emerging Markets Index (Index returns do not reflect deductions for fees, expenses or taxes, including taxes on foreign dividends)	37.75%	4.73%	4.87%	Aug. 25, 2008

[1] The expense information in the fee table has been restated to reflect a reduction in the Fund’s Investment Advisory Fee rate, effective June 1, 2017. As such, the Total Annual Fund Operating Expenses may not correlate to the expense ratios in the Fund’s financial highlights and financial statements, which include the prior Investment Advisory Fee rate.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Emerging Markets Equity Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  EMERGING MARKETS EQUITY FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Emerging Markets Equity Fund (the “Fund”) is to seek to achieve capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 41% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

41.00%

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

The expense information in the fee table has been restated to reflect a reduction in the Fund's Investment Advisory Fee rate, effective June 1, 2017.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities located in emerging market countries. For this Fund, an issuer is considered to be located in an emerging market country if, at the time of investment: (i) its principal securities trading market is in an emerging market country, (ii) alone or on a consolidated basis it derives 50% or more of its annual revenue or profits from goods produced, sales made or services performed in emerging market countries or it has at least 50% of its assets in emerging markets countries, or (iii) it is organized under the laws of, or has a principal office in, an emerging market country. By applying this test, it is possible that a particular issuer could be deemed to be from more than one emerging market country.

The Sub-Adviser considers emerging market countries to be countries that major international financial institutions, such as the World Bank, or the Fund’s benchmark index generally consider to be less economically mature than developed nations, such as the United States or most nations in Western Europe. Emerging market countries can include every nation in the world except the United States, Canada, Japan, Australia, New Zealand and most nations located in Western Europe. Allocation of the Fund’s investments will depend upon the relative attractiveness of emerging countries and particular issuers. There are no prescribed limits on the geographic distribution of the Fund’s investments.

The investment process takes into account information about environmental, social and governance issues (also referred to as ESG) when making investment decisions. The Sub-Adviser focuses on engaging company management around corporate governance practices as well as what the Sub-Adviser deems to be materially important environmental and/or social issues facing a company.

The Sub-Adviser seeks to maximize returns by investing in growth-oriented equity securities of emerging country issuers. The Sub-Adviser combines top-down country criteria to allocate the Fund’s assets among countries (based on relative economic, political and social fundamentals, stock valuations, and investor sentiment) with bottom-up fundamental analysis of issuers (seeking to identify issuers with strong earnings growth potential). The Sub-Adviser attempts to manage the overall risk of its investments through its emphasis on thorough macroeconomic and fundamental research.

The Fund invests primarily in equity securities, including common stocks and convertible securities. The Fund may invest in securities of micro-, small-, medium- and large-capitalization companies. The Fund may invest in derivative instruments, including futures, options, swaps and forward foreign currency exchange contracts. The Fund may, but is not required to, use these derivative instruments for a variety of purposes, including hedging, risk management, portfolio management and to earn income. Derivative instruments used by the Fund will be counted toward the Fund’s 80% policy discussed above to the extent they have economic characteristics similar to the securities included within that policy.

The Fund may buy and sell portfolio securities actively. If it does, its portfolio turnover rate and transaction costs will rise, which may lower Fund performance.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Convertible Securities Risk.  The possibility that the value of the Fund’s investments in convertible securities may be adversely affected by changes in interest rates, the credit of the issuer and the value of the underlying common stock. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. In addition, as the market price of the underlying common stock declines below the conversion price, the price of the convertible security tends to be increasingly influenced by the yield of the convertible security.

Credit Risk.  The possibility that the counterparty to a derivatives contract held by the Fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that the Fund’s use of derivatives, such as futures, options, swap agreements and forward foreign currency exchange contracts, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Sub-Adviser believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that the Fund’s investments in securities of companies perceived to be “growth” companies may underperform when the Fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

Interest Rate Risk.  The possibility that the prices of the Fund’s convertible securities will decline due to rising interest rates.

Large-Cap Securities Risk.  The possibility that the Fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Micro-Cap Securities Risk.  The possibility that the return on the Fund’s investments in micro-cap companies may be less than the return on investments in stocks of larger companies or the stock market as a whole. Stock prices of micro-cap companies may be based in substantial part on future expectations rather than current achievements and may move sharply, especially during market upturns and downturns. Micro-cap companies are followed by relatively few securities analysts, and there tends to be less publicly available information about these companies. Micro-cap companies are more likely to be newly formed or in the early stages of development, depend on a few key employees, and have relatively limited product lines, markets or financial resources compared to larger capitalization companies.

Portfolio Turnover Risk.  The possibility that the Fund may frequently buy and sell portfolio securities, which may increase transaction costs to the Fund and cause the Fund’s performance to be less than you expect.

Small- and Mid-Cap Securities Risk.  The possibility that the Fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and the Fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in emerging market equity securities in the hope of achieving capital appreciation.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
34.74%	-19.38%
6/30/2009	9/30/2011

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Emerging Markets Equity Fund | Emerging Markets Equity Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.92%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.49%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.41%

^[1]

1 Year

rr_ExpenseExampleYear01

$ 144

3 Years

rr_ExpenseExampleYear03

446

5 Years

rr_ExpenseExampleYear05

771

10 Years

rr_ExpenseExampleYear10

$ 1,691

2009

rr_AnnualReturn2009

65.64%

2010

rr_AnnualReturn2010

19.15%

2011

rr_AnnualReturn2011

(18.44%)

2012

rr_AnnualReturn2012

19.61%

2013

rr_AnnualReturn2013

(1.13%)

2014

rr_AnnualReturn2014

(4.91%)

2015

rr_AnnualReturn2015

(10.89%)

2016

rr_AnnualReturn2016

5.80%

2017

rr_AnnualReturn2017

35.03%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

34.74%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(19.38%)

1 Year

rr_AverageAnnualReturnYear01

35.03%

5 Years

rr_AverageAnnualReturnYear05

3.66%

Since Inception

rr_AverageAnnualReturnSinceInception

3.55%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Emerging Markets Equity Fund | MSCI Emerging Markets Index (Index returns do not reflect deductions for fees, expenses or taxes, including taxes on foreign dividends)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

37.75%

5 Years

rr_AverageAnnualReturnYear05

4.73%

Since Inception

rr_AverageAnnualReturnSinceInception

4.87%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

[1] The expense information in the fee table has been restated to reflect a reduction in the Fund’s Investment Advisory Fee rate, effective June 1, 2017. As such, the Total Annual Fund Operating Expenses may not correlate to the expense ratios in the Fund’s financial highlights and financial statements, which include the prior Investment Advisory Fee rate.

XML

Penn Series Real Estate Securities Fund

FUND SUMMARY:  REAL ESTATE SECURITIES FUND

Investment Objective

The investment objective of the Real Estate Securities Fund (the “Fund”) is to achieve a high total return consistent with reasonable investment risks.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Real Estate Securities Fund Real Estate Securities Fund
Investment Advisory Fees	0.70%
Distribution (12b-1) Fees	none
Other Expenses	0.25%
Total Annual Fund Operating Expenses	0.95%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Real Estate Securities Fund | Real Estate Securities Fund | USD ($)	97	303	525	1,166

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 75% of the average value of its portfolio.

Principal Investment Strategy

Under normal circumstances, the Fund invests at least 80%, and normally substantially all, of its net assets, plus the amount of any borrowings for investment purposes, in common stocks and other equity securities issued by real estate companies, including real estate investment trusts (“REITs”). The Fund considers companies real estate companies if such companies (i) derive at least 50% of their revenues from the ownership, construction, financing, management or sale of commercial, industrial, or residential real estate; or (ii) have at least 50% of their assets in such real estate. REITs are companies that own interests in real estate or in real estate related loans or other interests, and their revenue primarily consists of rent derived from owned, income producing real estate properties and capital gains from the sale of such properties. A REIT in the U.S. is generally not taxed on income distributed to shareholders so long as it meets certain tax related requirements, including the requirement that it distribute substantially all of its taxable income to its shareholders. REIT-like entities are organized outside of the U.S. and have operations and receive foreign tax treatment similar to that of U.S. REITs. The Fund retains the ability to invest in real estate companies of any market capitalization. The Fund may invest up to 25% of its total assets in securities of foreign issuers which meet the same criteria for investment as domestic companies, or sponsored and unsponsored depositary receipts for such securities. Depositary receipts may take the form of ADRs, GDRs and EDRs. In managing the Fund’s portfolio, the Sub-Adviser adheres to an integrated, bottom-up, relative value investment process.

The Fund may buy and sell portfolio securities actively. If it does, its portfolio turnover rate and transaction costs will rise, which may lower Fund performance.

Principal Risks of Investing

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Concentration Risk.  The possibility that, to the extent the Fund invests to a significant extent in a particular industry or group of industries within a particular sector, the Fund may be subject to greater risks than if its investments were broadly diversified across industries and sectors. The Fund also is subject to loss due to adverse occurrences that may affect that industry or group of industries.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Portfolio Turnover Risk.  The possibility that the Fund may frequently buy and sell portfolio securities, which may increase transaction costs to the Fund and cause the Fund’s performance to be less than you expect.

Real Estate Securities Risk.  The possibility that the Fund’s investments in real estate securities, including REITs, may make the Fund more susceptible to the risks associated with direct investments in real estate. These risks include, among others, declines in the value of real estate; risks related to general and local economic conditions; changes in the availability, cost and terms of mortgage funds; loss of rental income due to vacancies; obsolescence of properties; overbuilding and increased competition; increases in property taxes and operating expenses; changes in zoning laws; defaults by borrowers or tenants, particularly during an economic downturn; and changes in interest rates. Any geographic concentration of the Fund’s real estate-related investments could result in the Fund being subject to the above risks to a greater degree.

REITs Risk.  The possibility that the Fund’s investments in REITs will subject the Fund to the risks associated with the direct ownership of real estate, including fluctuations in the value of underlying properties, changes in interest rates and risks related to general or local economic conditions. REITs are dependent upon management skills and generally may not be diversified. REITs are also subject to heavy cash flow dependency, defaults by borrowers or tenants and self-liquidation.

Small- and Mid-Cap Securities Risk.  The possibility that the Fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and the Fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of real estate and real estate related investing in the hope of realizing capital appreciation while diversifying their investment portfolio.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Performance prior to May 1, 2011 reflects the Fund’s investment performance when managed by a previous sub-adviser pursuant to a substantially similar principal investment strategy. Since May 1, 2011, Cohen & Steers Capital Management, Inc. (“Cohen & Steers”) has been responsible for the Fund’s day-to-day portfolio management. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
30.58%	-40.76%
9/30/2009	12/31/2008

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Real Estate Securities Fund	1 Year	5 Years	10 Years
Real Estate Securities Fund	7.40%	9.87%	6.68%
FTSE NAREIT Equity REIT Index (reflects no deduction for fees, expenses or taxes)	5.23%	9.46%	7.44%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Real Estate Securities Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  REAL ESTATE SECURITIES FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Real Estate Securities Fund (the “Fund”) is to achieve a high total return consistent with reasonable investment risks.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 75% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

75.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80%, and normally substantially all, of its net assets, plus the amount of any borrowings for investment purposes, in common stocks and other equity securities issued by real estate companies, including real estate investment trusts (“REITs”). The Fund considers companies real estate companies if such companies (i) derive at least 50% of their revenues from the ownership, construction, financing, management or sale of commercial, industrial, or residential real estate; or (ii) have at least 50% of their assets in such real estate. REITs are companies that own interests in real estate or in real estate related loans or other interests, and their revenue primarily consists of rent derived from owned, income producing real estate properties and capital gains from the sale of such properties. A REIT in the U.S. is generally not taxed on income distributed to shareholders so long as it meets certain tax related requirements, including the requirement that it distribute substantially all of its taxable income to its shareholders. REIT-like entities are organized outside of the U.S. and have operations and receive foreign tax treatment similar to that of U.S. REITs. The Fund retains the ability to invest in real estate companies of any market capitalization. The Fund may invest up to 25% of its total assets in securities of foreign issuers which meet the same criteria for investment as domestic companies, or sponsored and unsponsored depositary receipts for such securities. Depositary receipts may take the form of ADRs, GDRs and EDRs. In managing the Fund’s portfolio, the Sub-Adviser adheres to an integrated, bottom-up, relative value investment process.

The Fund may buy and sell portfolio securities actively. If it does, its portfolio turnover rate and transaction costs will rise, which may lower Fund performance.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Concentration Risk.  The possibility that, to the extent the Fund invests to a significant extent in a particular industry or group of industries within a particular sector, the Fund may be subject to greater risks than if its investments were broadly diversified across industries and sectors. The Fund also is subject to loss due to adverse occurrences that may affect that industry or group of industries.

Currency Risk.  The possibility that the value of the Fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

Liquidity Risk.  The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk.  The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub-Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Portfolio Turnover Risk.  The possibility that the Fund may frequently buy and sell portfolio securities, which may increase transaction costs to the Fund and cause the Fund’s performance to be less than you expect.

Real Estate Securities Risk.  The possibility that the Fund’s investments in real estate securities, including REITs, may make the Fund more susceptible to the risks associated with direct investments in real estate. These risks include, among others, declines in the value of real estate; risks related to general and local economic conditions; changes in the availability, cost and terms of mortgage funds; loss of rental income due to vacancies; obsolescence of properties; overbuilding and increased competition; increases in property taxes and operating expenses; changes in zoning laws; defaults by borrowers or tenants, particularly during an economic downturn; and changes in interest rates. Any geographic concentration of the Fund’s real estate-related investments could result in the Fund being subject to the above risks to a greater degree.

REITs Risk.  The possibility that the Fund’s investments in REITs will subject the Fund to the risks associated with the direct ownership of real estate, including fluctuations in the value of underlying properties, changes in interest rates and risks related to general or local economic conditions. REITs are dependent upon management skills and generally may not be diversified. REITs are also subject to heavy cash flow dependency, defaults by borrowers or tenants and self-liquidation.

Small- and Mid-Cap Securities Risk.  The possibility that the Fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and the Fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of real estate and real estate related investing in the hope of realizing capital appreciation while diversifying their investment portfolio.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. Performance prior to May 1, 2011 reflects the Fund’s investment performance when managed by a previous sub-adviser pursuant to a substantially similar principal investment strategy. Since May 1, 2011, Cohen & Steers Capital Management, Inc. (“Cohen & Steers”) has been responsible for the Fund’s day-to-day portfolio management. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
30.58%	-40.76%
9/30/2009	12/31/2008

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Real Estate Securities Fund | Real Estate Securities Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.70%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.25%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.95%

1 Year

rr_ExpenseExampleYear01

$ 97

3 Years

rr_ExpenseExampleYear03

303

5 Years

rr_ExpenseExampleYear05

525

10 Years

rr_ExpenseExampleYear10

$ 1,166

2008

rr_AnnualReturn2008

(39.38%)

2009

rr_AnnualReturn2009

26.54%

2010

rr_AnnualReturn2010

25.14%

2011

rr_AnnualReturn2011

7.04%

2012

rr_AnnualReturn2012

16.00%

2013

rr_AnnualReturn2013

3.13%

2014

rr_AnnualReturn2014

30.22%

2015

rr_AnnualReturn2015

5.22%

2016

rr_AnnualReturn2016

5.49%

2017

rr_AnnualReturn2017

7.40%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

30.58%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(40.76%)

1 Year

rr_AverageAnnualReturnYear01

7.40%

5 Years

rr_AverageAnnualReturnYear05

9.87%

10 Years

rr_AverageAnnualReturnYear10

6.68%

Penn Series Real Estate Securities Fund | FTSE NAREIT Equity REIT Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

5.23%

5 Years

rr_AverageAnnualReturnYear05

9.46%

10 Years

rr_AverageAnnualReturnYear10

7.44%

XML

Penn Series Aggressive Allocation Fund

FUND SUMMARY:  AGGRESSIVE ALLOCATION FUND

Investment Objective

The investment objective of the Aggressive Allocation Fund (the “Fund”) is to seek to achieve long-term capital growth consistent with its asset allocation strategy.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Aggressive Allocation Fund Aggressive Allocation Fund
Investment Advisory Fees	0.12%
Distribution (12b-1) Fees	none
Other Expenses	0.19%
Acquired Fund Fees and Expenses	0.97%
Total Annual Fund Operating Expenses	1.28%	[1]

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Aggressive Allocation Fund | Aggressive Allocation Fund | USD ($)	130	406	702	1,545

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 20% of the average value of its portfolio.

Principal Investment Strategy

The Fund seeks to achieve its investment objective by using a “fund-of-funds” strategy. Accordingly, the Fund invests in a combination of other Penn Series Funds (each, an “underlying fund” and, collectively, the “underlying funds”) in accordance with its target asset allocations. These underlying funds invest their assets directly in equity, fixed income, money market and other securities in accordance with their own investment objectives and policies. The underlying funds are managed using both indexed and active management strategies.

The Fund has its own distinct target portfolio allocation and is designed to accommodate specific investment goals and risk tolerances. Through its investments in the underlying funds, the Fund’s target allocation is intended to allocate the Fund’s assets among various asset classes, such as equity securities, fixed income securities and money market securities. The portfolio of the Fund is more heavily allocated to stocks, and reflects an aggressive approach.

In determining the asset allocation of the Fund, the Adviser will rely on the experience of its investment personnel and its evaluation of the overall financial markets, including, but not limited to, information about the economy, interest rates, and the long-term absolute and relative returns of various asset classes. Consideration will also be given to the investment styles of the managers of the underlying funds and their historic patterns of performance relative to their asset class and to other underlying funds. Periodic changes in allocations among the underlying funds will be based on information about the financial markets, changes within particular underlying funds, or the introduction of new Penn Series Funds that would, in the Adviser’s opinion, enhance the return potential of the Fund. These changes will be implemented as necessary, recognizing that these decisions tend to be long-term in nature, based on information about the financial markets and on the Fund’s investment objective.

The following chart shows the Fund’s target asset allocation among the various asset classes. The Adviser may permit modest deviations from the target asset allocations listed below. Accordingly, the Fund’s actual allocations may differ from this illustration.

Asset Class	Target Asset Allocation
Equity Funds	85% - 100%
Fixed Income and Money Market Funds	0% - 15%

The Adviser reserves the right to modify the Fund’s target asset allocations and to substitute other underlying funds and add additional underlying funds from time to time should circumstances warrant a change. The Adviser may periodically rebalance the Fund’s investments in the underlying funds to bring the Fund back within its target range.

Principal Risks

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Asset Allocation Risk.  The possibility that the Fund may underperform other funds with similar investment objectives due to the Fund’s allocation of assets to underlying funds investing in asset classes or market sectors that perform poorly relative to other asset categories.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Underlying Fund Investment Risk.  The possibility that the underperformance of an underlying fund may contribute to the underperformance of the Fund. The Fund’s performance and risks will be directly related to the performance and risks of the underlying funds in which it invests. In addition, the Fund indirectly pays a pro rata portion of the expenses incurred by the underlying funds, which also may lower the Fund’s performance.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by an underlying fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by an underlying fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by an underlying fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of an underlying fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that an underlying fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Adviser or Sub-Adviser of the underlying fund believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that an underlying fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that an underlying fund’s investments in securities of companies perceived to be “growth” companies may underperform when the underlying fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

High Yield Bond Risk.  The possibility that an underlying fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the underlying fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to the underlying fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Interest Rate Risk.  The possibility that the prices of an underlying fund’s fixed income investments will decline due to rising interest rates.

Investment Risk.  You may lose money by investing in the Money Market Fund. Although the Money Market Fund seeks to preserve the value of your investment at $1.00 per share, there is no guarantee that the Money Market Fund will be able to do so. An investment in the Money Market Fund is not insured or guaranteed by the FDIC or any other government agency. PMAM, the Fund’s sponsor, and its affiliates have no legal obligation to provide financial support to the Money Market Fund, and you should not expect that PMAM or its affiliates will provide financial support to the Money Market Fund at any time.

Large-Cap Securities Risk.  The possibility that an underlying fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of an underlying fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If an underlying fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Portfolio Turnover Risk.  The possibility that an underlying fund may frequently buy and sell portfolio securities, which may increase transaction costs to the underlying fund and cause the underlying fund’s performance to be less than you expect.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing an underlying fund to invest in fixed income securities with lower interest rates, which may adversely affect the underlying fund’s performance.

Small- and Mid-Cap Securities Risk.  The possibility that an underlying fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and an underlying fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by an underlying fund if it is not obligated to do because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause an underlying fund’s share price or yield to fall.

“Value” Investing Risk.  The possibility that an underlying fund’s investments in securities perceived to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which an underlying fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the underlying fund’s investment style shifts out of favor.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index and one additional index, the Bloomberg Barclays Capital U.S. Aggregate Bond Index. The Bloomberg Barclays Capital U.S. Aggregate Bond Index, in conjunction with the broad-based index, is used to track the broad range of allocations the Fund makes to the underlying funds. The foregoing indices, when considered together, may provide investors with a useful comparison of the Fund’s overall performance. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
17.31%	-16.51%
6/30/2009	9/30/2011

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Aggressive Allocation Fund	1 Year	5 Years	Since Inception	Inception Date
Aggressive Allocation Fund	20.08%	10.68%	7.41%	Aug. 25, 2008
Russell 3000® Index (reflects no deduction for fees, expenses or taxes)	21.13%	15.58%	10.45%	Aug. 25, 2008
Bloomberg Barclays Capital U.S. Aggregate Bond Index (reflects no deduction for fees, expenses or taxes)	3.54%	2.10%	4.13%	Aug. 25, 2008

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Aggressive Allocation Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  AGGRESSIVE ALLOCATION FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Aggressive Allocation Fund (the “Fund”) is to seek to achieve long-term capital growth consistent with its asset allocation strategy.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 20% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

20.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund seeks to achieve its investment objective by using a “fund-of-funds” strategy. Accordingly, the Fund invests in a combination of other Penn Series Funds (each, an “underlying fund” and, collectively, the “underlying funds”) in accordance with its target asset allocations. These underlying funds invest their assets directly in equity, fixed income, money market and other securities in accordance with their own investment objectives and policies. The underlying funds are managed using both indexed and active management strategies.

The Fund has its own distinct target portfolio allocation and is designed to accommodate specific investment goals and risk tolerances. Through its investments in the underlying funds, the Fund’s target allocation is intended to allocate the Fund’s assets among various asset classes, such as equity securities, fixed income securities and money market securities. The portfolio of the Fund is more heavily allocated to stocks, and reflects an aggressive approach.

In determining the asset allocation of the Fund, the Adviser will rely on the experience of its investment personnel and its evaluation of the overall financial markets, including, but not limited to, information about the economy, interest rates, and the long-term absolute and relative returns of various asset classes. Consideration will also be given to the investment styles of the managers of the underlying funds and their historic patterns of performance relative to their asset class and to other underlying funds. Periodic changes in allocations among the underlying funds will be based on information about the financial markets, changes within particular underlying funds, or the introduction of new Penn Series Funds that would, in the Adviser’s opinion, enhance the return potential of the Fund. These changes will be implemented as necessary, recognizing that these decisions tend to be long-term in nature, based on information about the financial markets and on the Fund’s investment objective.

The following chart shows the Fund’s target asset allocation among the various asset classes. The Adviser may permit modest deviations from the target asset allocations listed below. Accordingly, the Fund’s actual allocations may differ from this illustration.

Asset Class	Target Asset Allocation
Equity Funds	85% - 100%
Fixed Income and Money Market Funds	0% - 15%

The Adviser reserves the right to modify the Fund’s target asset allocations and to substitute other underlying funds and add additional underlying funds from time to time should circumstances warrant a change. The Adviser may periodically rebalance the Fund’s investments in the underlying funds to bring the Fund back within its target range.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Asset Allocation Risk.  The possibility that the Fund may underperform other funds with similar investment objectives due to the Fund’s allocation of assets to underlying funds investing in asset classes or market sectors that perform poorly relative to other asset categories.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Underlying Fund Investment Risk.  The possibility that the underperformance of an underlying fund may contribute to the underperformance of the Fund. The Fund’s performance and risks will be directly related to the performance and risks of the underlying funds in which it invests. In addition, the Fund indirectly pays a pro rata portion of the expenses incurred by the underlying funds, which also may lower the Fund’s performance.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by an underlying fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by an underlying fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by an underlying fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of an underlying fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that an underlying fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Adviser or Sub-Adviser of the underlying fund believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Emerging Markets Risk.  The possibility that the stocks of companies located in emerging markets may be more volatile, and less liquid, than the stocks of companies located in the U.S. and developed foreign markets due to political, economic, or regulatory conditions within emerging market countries. In addition, emerging market countries may experience more volatile interest and currency exchange rates, higher levels of inflation and less efficient trading and settlement systems.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that an underlying fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that an underlying fund’s investments in securities of companies perceived to be “growth” companies may underperform when the underlying fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

High Yield Bond Risk.  The possibility that an underlying fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the underlying fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to the underlying fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Interest Rate Risk.  The possibility that the prices of an underlying fund’s fixed income investments will decline due to rising interest rates.

Investment Risk.  You may lose money by investing in the Money Market Fund. Although the Money Market Fund seeks to preserve the value of your investment at $1.00 per share, there is no guarantee that the Money Market Fund will be able to do so. An investment in the Money Market Fund is not insured or guaranteed by the FDIC or any other government agency. PMAM, the Fund’s sponsor, and its affiliates have no legal obligation to provide financial support to the Money Market Fund, and you should not expect that PMAM or its affiliates will provide financial support to the Money Market Fund at any time.

Large-Cap Securities Risk.  The possibility that an underlying fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of an underlying fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If an underlying fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Portfolio Turnover Risk.  The possibility that an underlying fund may frequently buy and sell portfolio securities, which may increase transaction costs to the underlying fund and cause the underlying fund’s performance to be less than you expect.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing an underlying fund to invest in fixed income securities with lower interest rates, which may adversely affect the underlying fund’s performance.

Small- and Mid-Cap Securities Risk.  The possibility that an underlying fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and an underlying fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by an underlying fund if it is not obligated to do because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause an underlying fund’s share price or yield to fall.

“Value” Investing Risk.  The possibility that an underlying fund’s investments in securities perceived to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which an underlying fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the underlying fund’s investment style shifts out of favor.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index and one additional index, the Bloomberg Barclays Capital U.S. Aggregate Bond Index. The Bloomberg Barclays Capital U.S. Aggregate Bond Index, in conjunction with the broad-based index, is used to track the broad range of allocations the Fund makes to the underlying funds. The foregoing indices, when considered together, may provide investors with a useful comparison of the Fund’s overall performance. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index and one additional index, the Bloomberg Barclays Capital U.S. Aggregate Bond Index.

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

The Bloomberg Barclays Capital U.S. Aggregate Bond Index, in conjunction with the broad-based index, is used to track the broad range of allocations the Fund makes to the underlying funds. The foregoing indices, when considered together, may provide investors with a useful comparison of the Fund’s overall performance.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
17.31%	-16.51%
6/30/2009	9/30/2011

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Aggressive Allocation Fund | Aggressive Allocation Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.12%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.19%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.97%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.28%

^[1]

1 Year

rr_ExpenseExampleYear01

$ 130

3 Years

rr_ExpenseExampleYear03

406

5 Years

rr_ExpenseExampleYear05

702

10 Years

rr_ExpenseExampleYear10

$ 1,545

2009

rr_AnnualReturn2009

28.94%

2010

rr_AnnualReturn2010

15.96%

2011

rr_AnnualReturn2011

(3.66%)

2012

rr_AnnualReturn2012

15.48%

2013

rr_AnnualReturn2013

22.49%

2014

rr_AnnualReturn2014

6.78%

2015

rr_AnnualReturn2015

(1.59%)

2016

rr_AnnualReturn2016

7.46%

2017

rr_AnnualReturn2017

20.08%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

17.31%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(16.51%)

1 Year

rr_AverageAnnualReturnYear01

20.08%

5 Years

rr_AverageAnnualReturnYear05

10.68%

Since Inception

rr_AverageAnnualReturnSinceInception

7.41%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Aggressive Allocation Fund | Russell 3000® Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

21.13%

5 Years

rr_AverageAnnualReturnYear05

15.58%

Since Inception

rr_AverageAnnualReturnSinceInception

10.45%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Aggressive Allocation Fund | Bloomberg Barclays Capital U.S. Aggregate Bond Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

3.54%

5 Years

rr_AverageAnnualReturnYear05

2.10%

Since Inception

rr_AverageAnnualReturnSinceInception

4.13%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Penn Series Moderately Aggressive Allocation Fund

FUND SUMMARY:  MODERATELY AGGRESSIVE ALLOCATION FUND

Investment Objective

The investment objective of the Moderately Aggressive Allocation Fund (the “Fund”) is to seek to achieve long-term capital growth and current income consistent with its asset allocation strategy.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Moderately Aggressive Allocation Fund Moderately Aggressive Allocation Fund
Investment Advisory Fees	0.12%
Distribution (12b-1) Fees	none
Other Expenses	0.17%
Acquired Fund Fees and Expenses	0.93%
Total Annual Fund Operating Expenses	1.22%	[1]

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Moderately Aggressive Allocation Fund | Moderately Aggressive Allocation Fund | USD ($)	124	387	670	1,477

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 16% of the average value of its portfolio.

Principal Investment Strategy

The Fund seeks to achieve its investment objective by using a “fund-of-funds” strategy. Accordingly, the Fund invests in a combination of other Penn Series Funds (each, an “underlying fund” and, collectively, the “underlying funds”) in accordance with its target asset allocations. These underlying funds invest their assets directly in equity, fixed income, money market and other securities in accordance with their own investment objectives and policies. The underlying funds are managed using both indexed and active management strategies.

The Fund has its own distinct target portfolio allocation and is designed to accommodate specific investment goals and risk tolerances. Through its investments in the underlying funds, the Fund’s target allocation is intended to allocate the Fund’s assets among various asset classes, such as equity securities, fixed income securities and money market securities. The portfolio of the Fund is more heavily allocated to stocks, and reflects a moderately aggressive approach.

In determining the asset allocation of the Fund, the Adviser will rely on the experience of its investment personnel and its evaluation of the overall financial markets, including, but not limited to, information about the economy, interest rates, and the long-term absolute and relative returns of various asset classes. Consideration will also be given to the investment styles of the managers of the underlying funds and their historic patterns of performance relative to their asset class and to other underlying funds. Periodic changes in allocations among the underlying funds will be based on information about the financial markets, changes within particular underlying funds, or the introduction of new Penn Series Funds that would, in the Adviser’s opinion, enhance the return potential of the Fund. These changes will be implemented as necessary, recognizing that these decisions tend to be long-term in nature, based on information about the financial markets and on the Fund’s investment objective.

The following chart shows the Fund’s target asset allocation among the various asset classes. The Adviser may permit modest deviations from the target asset allocations listed below. Accordingly, the Fund’s actual allocations may differ from this illustration.

Asset Class	Target Asset Allocation
Equity Funds	70% - 100%
Fixed Income and Money Market Funds	0% - 30%

The Adviser reserves the right to modify the Fund’s target asset allocations and to substitute other underlying funds and add additional underlying funds from time to time should circumstances warrant a change. The Adviser may periodically rebalance the Fund’s investments in the underlying funds to bring the Fund back within its target range.

Principal Risks

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Asset Allocation Risk.  The possibility that the Fund may underperform other funds with similar investment objectives due to the Fund’s allocation of assets to underlying funds investing in asset classes or market sectors that perform poorly relative to other asset categories.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Underlying Fund Investment Risk.  The possibility that the underperformance of an underlying fund may contribute to the underperformance of the Fund. The Fund’s performance and risks will be directly related to the performance and risks of the underlying funds in which it invests. In addition, the Fund indirectly pays a pro rata portion of the expenses incurred by the underlying funds, which also may lower the Fund’s performance.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by an underlying fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by an underlying fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by an underlying fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of an underlying fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that an underlying fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Adviser or Sub-Adviser of the underlying fund believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that an underlying fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that an underlying fund’s investments in securities of companies perceived to be “growth” companies may underperform when the underlying fund’s investment strategy shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

High Yield Bond Risk.  The possibility that an underlying fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the underlying fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to the underlying fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Interest Rate Risk.  The possibility that the prices of an underlying fund’s fixed income investments will decline due to rising interest rates.

Investment Risk.  You may lose money by investing in the Money Market Fund. Although the Money Market Fund seeks to preserve the value of your investment at $1.00 per share, there is no guarantee that the Money Market Fund will be able to do so. An investment in the Money Market Fund is not insured or guaranteed by the FDIC or any other government agency. PMAM, the Fund’s sponsor, and its affiliates have no legal obligation to provide financial support to the Money Market Fund, and you should not expect that PMAM or its affiliates will provide financial support to the Money Market Fund at any time.

Large-Cap Securities Risk.  The possibility that an underlying fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of an underlying fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If an underlying fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Portfolio Turnover Risk.  The possibility that an underlying fund may frequently buy and sell portfolio securities, which may increase transaction costs to the underlying fund and cause the underlying fund’s performance to be less than you expect.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing an underlying fund to invest in fixed income securities with lower interest rates, which may adversely affect the underlying fund’s performance.

Small- and Mid-Cap Securities Risk.  The possibility that an underlying fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and an underlying fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by an underlying fund if it is not obligated to do because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause an underlying fund’s share price or yield to fall.

“Value” Investing Risk.  The possibility that an underlying fund’s investments in securities perceived to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which an underlying fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the underlying fund’s investment style shifts out of favor.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index and one additional index, the Bloomberg Barclays Capital U.S. Aggregate Bond Index. The Bloomberg Barclays Capital U.S. Aggregate Bond Index, in conjunction with the broad-based index, is used to track the broad range of allocations the Fund makes to the underlying funds. The foregoing indices, when considered together, may provide investors with a useful comparison of the Fund’s overall performance. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
14.52%	-13.53%
9/30/2009	9/30/2011

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Moderately Aggressive Allocation Fund	1 Year	5 Years	Since Inception	Inception Date
Moderately Aggressive Allocation Fund	17.58%	9.62%	7.73%	Aug. 25, 2008
Russell 3000® Index (reflects no deduction for fees, expenses or taxes)	21.13%	15.58%	10.45%	Aug. 25, 2008
Bloomberg Barclays Capital U.S. Aggregate Bond Index (reflects no deduction for fees, expenses or taxes)	3.54%	2.10%	4.13%	Aug. 25, 2008

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Moderately Aggressive Allocation Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  MODERATELY AGGRESSIVE ALLOCATION FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Moderately Aggressive Allocation Fund (the “Fund”) is to seek to achieve long-term capital growth and current income consistent with its asset allocation strategy.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 16% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

16.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund seeks to achieve its investment objective by using a “fund-of-funds” strategy. Accordingly, the Fund invests in a combination of other Penn Series Funds (each, an “underlying fund” and, collectively, the “underlying funds”) in accordance with its target asset allocations. These underlying funds invest their assets directly in equity, fixed income, money market and other securities in accordance with their own investment objectives and policies. The underlying funds are managed using both indexed and active management strategies.

The Fund has its own distinct target portfolio allocation and is designed to accommodate specific investment goals and risk tolerances. Through its investments in the underlying funds, the Fund’s target allocation is intended to allocate the Fund’s assets among various asset classes, such as equity securities, fixed income securities and money market securities. The portfolio of the Fund is more heavily allocated to stocks, and reflects a moderately aggressive approach.

In determining the asset allocation of the Fund, the Adviser will rely on the experience of its investment personnel and its evaluation of the overall financial markets, including, but not limited to, information about the economy, interest rates, and the long-term absolute and relative returns of various asset classes. Consideration will also be given to the investment styles of the managers of the underlying funds and their historic patterns of performance relative to their asset class and to other underlying funds. Periodic changes in allocations among the underlying funds will be based on information about the financial markets, changes within particular underlying funds, or the introduction of new Penn Series Funds that would, in the Adviser’s opinion, enhance the return potential of the Fund. These changes will be implemented as necessary, recognizing that these decisions tend to be long-term in nature, based on information about the financial markets and on the Fund’s investment objective.

The following chart shows the Fund’s target asset allocation among the various asset classes. The Adviser may permit modest deviations from the target asset allocations listed below. Accordingly, the Fund’s actual allocations may differ from this illustration.

Asset Class	Target Asset Allocation
Equity Funds	70% - 100%
Fixed Income and Money Market Funds	0% - 30%

The Adviser reserves the right to modify the Fund’s target asset allocations and to substitute other underlying funds and add additional underlying funds from time to time should circumstances warrant a change. The Adviser may periodically rebalance the Fund’s investments in the underlying funds to bring the Fund back within its target range.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Asset Allocation Risk.  The possibility that the Fund may underperform other funds with similar investment objectives due to the Fund’s allocation of assets to underlying funds investing in asset classes or market sectors that perform poorly relative to other asset categories.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Underlying Fund Investment Risk.  The possibility that the underperformance of an underlying fund may contribute to the underperformance of the Fund. The Fund’s performance and risks will be directly related to the performance and risks of the underlying funds in which it invests. In addition, the Fund indirectly pays a pro rata portion of the expenses incurred by the underlying funds, which also may lower the Fund’s performance.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by an underlying fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by an underlying fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by an underlying fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of an underlying fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that an underlying fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Adviser or Sub-Adviser of the underlying fund believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that an underlying fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that an underlying fund’s investments in securities of companies perceived to be “growth” companies may underperform when the underlying fund’s investment strategy shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

High Yield Bond Risk.  The possibility that an underlying fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the underlying fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to the underlying fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Interest Rate Risk.  The possibility that the prices of an underlying fund’s fixed income investments will decline due to rising interest rates.

Investment Risk.  You may lose money by investing in the Money Market Fund. Although the Money Market Fund seeks to preserve the value of your investment at $1.00 per share, there is no guarantee that the Money Market Fund will be able to do so. An investment in the Money Market Fund is not insured or guaranteed by the FDIC or any other government agency. PMAM, the Fund’s sponsor, and its affiliates have no legal obligation to provide financial support to the Money Market Fund, and you should not expect that PMAM or its affiliates will provide financial support to the Money Market Fund at any time.

Large-Cap Securities Risk.  The possibility that an underlying fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of an underlying fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If an underlying fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Portfolio Turnover Risk.  The possibility that an underlying fund may frequently buy and sell portfolio securities, which may increase transaction costs to the underlying fund and cause the underlying fund’s performance to be less than you expect.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing an underlying fund to invest in fixed income securities with lower interest rates, which may adversely affect the underlying fund’s performance.

Small- and Mid-Cap Securities Risk.  The possibility that an underlying fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and an underlying fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by an underlying fund if it is not obligated to do because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause an underlying fund’s share price or yield to fall.

“Value” Investing Risk.  The possibility that an underlying fund’s investments in securities perceived to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which an underlying fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the underlying fund’s investment style shifts out of favor.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index and one additional index, the Bloomberg Barclays Capital U.S. Aggregate Bond Index. The Bloomberg Barclays Capital U.S. Aggregate Bond Index, in conjunction with the broad-based index, is used to track the broad range of allocations the Fund makes to the underlying funds. The foregoing indices, when considered together, may provide investors with a useful comparison of the Fund’s overall performance. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index and one additional index, the Bloomberg Barclays Capital U.S. Aggregate Bond Index.

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

The Bloomberg Barclays Capital U.S. Aggregate Bond Index, in conjunction with the broad-based index, is used to track the broad range of allocations the Fund makes to the underlying funds. The foregoing indices, when considered together, may provide investors with a useful comparison of the Fund’s overall performance.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
14.52%	-13.53%
9/30/2009	9/30/2011

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Moderately Aggressive Allocation Fund | Moderately Aggressive Allocation Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.12%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.17%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.93%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.22%

^[1]

1 Year

rr_ExpenseExampleYear01

$ 124

3 Years

rr_ExpenseExampleYear03

387

5 Years

rr_ExpenseExampleYear05

670

10 Years

rr_ExpenseExampleYear10

$ 1,477

2009

rr_AnnualReturn2009

27.25%

2010

rr_AnnualReturn2010

14.51%

2011

rr_AnnualReturn2011

(1.80%)

2012

rr_AnnualReturn2012

13.63%

2013

rr_AnnualReturn2013

19.16%

2014

rr_AnnualReturn2014

6.28%

2015

rr_AnnualReturn2015

(1.14%)

2016

rr_AnnualReturn2016

7.52%

2017

rr_AnnualReturn2017

17.58%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

14.52%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(13.53%)

1 Year

rr_AverageAnnualReturnYear01

17.58%

5 Years

rr_AverageAnnualReturnYear05

9.62%

Since Inception

rr_AverageAnnualReturnSinceInception

7.73%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Moderately Aggressive Allocation Fund | Russell 3000® Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

21.13%

5 Years

rr_AverageAnnualReturnYear05

15.58%

Since Inception

rr_AverageAnnualReturnSinceInception

10.45%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Moderately Aggressive Allocation Fund | Bloomberg Barclays Capital U.S. Aggregate Bond Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

3.54%

5 Years

rr_AverageAnnualReturnYear05

2.10%

Since Inception

rr_AverageAnnualReturnSinceInception

4.13%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Penn Series Moderate Allocation Fund

FUND SUMMARY:  MODERATE ALLOCATION FUND

Investment Objective

The investment objective of the Moderate Allocation Fund (the “Fund”) is to seek to achieve long-term capital growth and current income consistent with its asset allocation strategy.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Moderate Allocation Fund Moderate Allocation Fund
Investment Advisory Fees	0.12%
Distribution (12b-1) Fees	none
Other Expenses	0.17%
Acquired Fund Fees and Expenses	0.86%
Total Annual Fund Operating Expenses	1.15%	[1]

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Moderate Allocation Fund | Moderate Allocation Fund | USD ($)	117	365	633	1,398

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 12% of the average value of its portfolio.

Principal Investment Strategy

The Fund seeks to achieve its investment objective by using a “fund-of-funds” strategy. Accordingly, the Fund invests in a combination of other Penn Series Funds (each, an “underlying fund” and, collectively, the “underlying funds”) in accordance with its target asset allocations. These underlying funds invest their assets directly in equity, fixed income, money market and other securities in accordance with their own investment objectives and policies. The underlying funds are managed using both indexed and active management strategies.

The Fund has its own distinct target portfolio allocation and is designed to accommodate specific investment goals and risk tolerances. Through its investments in the underlying funds, the Fund’s target allocation is intended to allocate the Fund’s assets among various asset classes, such as equity securities, fixed income securities and money market securities. The portfolio of the Fund is allocated among stock, bond and cash investments with a majority of its assets allocated to stocks, and is designed to offer investors an investment option that is less aggressive than the Penn Series Aggressive Allocation and Moderately Aggressive Allocation Funds, but more aggressive than the Penn Series Moderately Conservative Allocation and Conservative Allocation Funds.

In determining the asset allocation of the Fund, the Adviser will rely on the experience of its investment personnel and its evaluation of the overall financial markets, including, but not limited to, information about the economy, interest rates, and the long-term absolute and relative returns of various asset classes. Consideration will also be given to the investment styles of the managers of the underlying funds and their historic patterns of performance relative to their asset class and to other underlying funds. Periodic changes in allocations among the underlying funds will be based on information about the financial markets, changes within particular underlying funds, or the introduction of new Penn Series Funds that would, in the Adviser’s opinion, enhance the return potential of the Fund. These changes will be implemented as necessary, recognizing that these decisions tend to be long-term in nature, based on information about the financial markets and on the Fund’s investment objective.

The following chart shows the Fund’s target asset allocation among the various asset classes. The Adviser may permit modest deviations from the target asset allocations listed below. Accordingly, the Fund’s actual allocations may differ from this illustration.

Asset Class	Target Asset Allocation
Equity Funds	50% - 70%
Fixed Income and Money Market Funds	30% - 50%

The Adviser reserves the right to modify the Fund’s target asset allocations and to substitute other underlying funds and add additional underlying funds from time to time should circumstances warrant a change. The Adviser may periodically rebalance the Fund’s investments in the underlying funds to bring the Fund back within its target range.

Principal Risks

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Asset Allocation Risk.  The possibility that the Fund may underperform other funds with similar investment objectives due to the Fund’s allocation of assets to underlying funds investing in asset classes or market sectors that perform poorly relative to other asset categories.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Underlying Fund Investment Risk.  The possibility that the underperformance of an underlying fund may contribute to the underperformance of the Fund. The Fund’s performance and risks will be directly related to the performance and risks of the underlying funds in which it invests. In addition, the Fund indirectly pays a pro rata portion of the expenses incurred by the underlying funds, which also may lower the Fund’s performance.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by an underlying fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by an underlying fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by an underlying fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of an underlying fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that an underlying fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Adviser or Sub-Adviser of the underlying fund believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that an underlying fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that an underlying fund’s investments in securities of companies perceived to be “growth” companies may underperform when the underlying fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

High Yield Bond Risk.  The possibility that an underlying fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the underlying fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to the underlying fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Interest Rate Risk.  The possibility that the prices of an underlying fund’s fixed income investments will decline due to rising interest rates.

Investment Risk.  You may lose money by investing in the Money Market Fund. Although the Money Market Fund seeks to preserve the value of your investment at $1.00 per share, there is no guarantee that the Money Market Fund will be able to do so. An investment in the Money Market Fund is not insured or guaranteed by the FDIC or any other government agency. PMAM, the Fund’s sponsor, and its affiliates have no legal obligation to provide financial support to the Money Market Fund, and you should not expect that PMAM or its affiliates will provide financial support to the Money Market Fund at any time.

Large-Cap Securities Risk.  The possibility that an underlying fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of an underlying fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If an underlying fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Portfolio Turnover Risk.  The possibility that an underlying fund may frequently buy and sell portfolio securities, which may increase transaction costs to the underlying fund and cause the underlying fund’s performance to be less than you expect.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing an underlying fund to invest in fixed income securities with lower interest rates, which may adversely affect the underlying fund’s performance.

Small- and Mid-Cap Securities Risk.  The possibility that an underlying fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and an underlying fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by an underlying fund if it is not obligated to do because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause an underlying fund’s share price or yield to fall.

“Value” Investing Risk.  The possibility that an underlying fund’s investments in securities perceived to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which an underlying fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the underlying fund’s investment style shifts out of favor.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index and one additional index, the Bloomberg Barclays Capital U.S. Aggregate Bond Index. The Bloomberg Barclays Capital U.S. Aggregate Bond Index, in conjunction with the broad-based index, is used to track the broad range of allocations the Fund makes to the underlying funds. The foregoing indices, when considered together, may provide investors with a useful comparison of the Fund’s overall performance. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
11.68%	-9.29%
6/30/2009	9/30/2011

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Moderate Allocation Fund	1 Year	5 Years	Since Inception	Inception Date
Moderate Allocation Fund	14.00%	7.89%	6.45%	Aug. 25, 2008
Russell 3000® Index (reflects no deduction for fees, expenses or taxes)	21.13%	15.58%	10.45%	Aug. 25, 2008
Bloomberg Barclays Capital U.S. Aggregate Bond Index (reflects no deduction for fees, expenses or taxes)	3.54%	2.10%	4.13%	Aug. 25, 2008

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Moderate Allocation Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  MODERATE ALLOCATION FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Moderate Allocation Fund (the “Fund”) is to seek to achieve long-term capital growth and current income consistent with its asset allocation strategy.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 12% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

12.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund seeks to achieve its investment objective by using a “fund-of-funds” strategy. Accordingly, the Fund invests in a combination of other Penn Series Funds (each, an “underlying fund” and, collectively, the “underlying funds”) in accordance with its target asset allocations. These underlying funds invest their assets directly in equity, fixed income, money market and other securities in accordance with their own investment objectives and policies. The underlying funds are managed using both indexed and active management strategies.

The Fund has its own distinct target portfolio allocation and is designed to accommodate specific investment goals and risk tolerances. Through its investments in the underlying funds, the Fund’s target allocation is intended to allocate the Fund’s assets among various asset classes, such as equity securities, fixed income securities and money market securities. The portfolio of the Fund is allocated among stock, bond and cash investments with a majority of its assets allocated to stocks, and is designed to offer investors an investment option that is less aggressive than the Penn Series Aggressive Allocation and Moderately Aggressive Allocation Funds, but more aggressive than the Penn Series Moderately Conservative Allocation and Conservative Allocation Funds.

In determining the asset allocation of the Fund, the Adviser will rely on the experience of its investment personnel and its evaluation of the overall financial markets, including, but not limited to, information about the economy, interest rates, and the long-term absolute and relative returns of various asset classes. Consideration will also be given to the investment styles of the managers of the underlying funds and their historic patterns of performance relative to their asset class and to other underlying funds. Periodic changes in allocations among the underlying funds will be based on information about the financial markets, changes within particular underlying funds, or the introduction of new Penn Series Funds that would, in the Adviser’s opinion, enhance the return potential of the Fund. These changes will be implemented as necessary, recognizing that these decisions tend to be long-term in nature, based on information about the financial markets and on the Fund’s investment objective.

The following chart shows the Fund’s target asset allocation among the various asset classes. The Adviser may permit modest deviations from the target asset allocations listed below. Accordingly, the Fund’s actual allocations may differ from this illustration.

Asset Class	Target Asset Allocation
Equity Funds	50% - 70%
Fixed Income and Money Market Funds	30% - 50%

The Adviser reserves the right to modify the Fund’s target asset allocations and to substitute other underlying funds and add additional underlying funds from time to time should circumstances warrant a change. The Adviser may periodically rebalance the Fund’s investments in the underlying funds to bring the Fund back within its target range.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Asset Allocation Risk.  The possibility that the Fund may underperform other funds with similar investment objectives due to the Fund’s allocation of assets to underlying funds investing in asset classes or market sectors that perform poorly relative to other asset categories.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Underlying Fund Investment Risk.  The possibility that the underperformance of an underlying fund may contribute to the underperformance of the Fund. The Fund’s performance and risks will be directly related to the performance and risks of the underlying funds in which it invests. In addition, the Fund indirectly pays a pro rata portion of the expenses incurred by the underlying funds, which also may lower the Fund’s performance.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by an underlying fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by an underlying fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by an underlying fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of an underlying fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that an underlying fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Adviser or Sub-Adviser of the underlying fund believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that an underlying fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that an underlying fund’s investments in securities of companies perceived to be “growth” companies may underperform when the underlying fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

High Yield Bond Risk.  The possibility that an underlying fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the underlying fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to the underlying fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Interest Rate Risk.  The possibility that the prices of an underlying fund’s fixed income investments will decline due to rising interest rates.

Investment Risk.  You may lose money by investing in the Money Market Fund. Although the Money Market Fund seeks to preserve the value of your investment at $1.00 per share, there is no guarantee that the Money Market Fund will be able to do so. An investment in the Money Market Fund is not insured or guaranteed by the FDIC or any other government agency. PMAM, the Fund’s sponsor, and its affiliates have no legal obligation to provide financial support to the Money Market Fund, and you should not expect that PMAM or its affiliates will provide financial support to the Money Market Fund at any time.

Large-Cap Securities Risk.  The possibility that an underlying fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of an underlying fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If an underlying fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Portfolio Turnover Risk.  The possibility that an underlying fund may frequently buy and sell portfolio securities, which may increase transaction costs to the underlying fund and cause the underlying fund’s performance to be less than you expect.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing an underlying fund to invest in fixed income securities with lower interest rates, which may adversely affect the underlying fund’s performance.

Small- and Mid-Cap Securities Risk.  The possibility that an underlying fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and an underlying fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by an underlying fund if it is not obligated to do because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause an underlying fund’s share price or yield to fall.

“Value” Investing Risk.  The possibility that an underlying fund’s investments in securities perceived to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which an underlying fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the underlying fund’s investment style shifts out of favor.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index and one additional index, the Bloomberg Barclays Capital U.S. Aggregate Bond Index. The Bloomberg Barclays Capital U.S. Aggregate Bond Index, in conjunction with the broad-based index, is used to track the broad range of allocations the Fund makes to the underlying funds. The foregoing indices, when considered together, may provide investors with a useful comparison of the Fund’s overall performance. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index and one additional index, the Bloomberg Barclays Capital U.S. Aggregate Bond Index.

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

The Bloomberg Barclays Capital U.S. Aggregate Bond Index, in conjunction with the broad-based index, is used to track the broad range of allocations the Fund makes to the underlying funds. The foregoing indices, when considered together, may provide investors with a useful comparison of the Fund’s overall performance.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
11.68%	-9.29%
6/30/2009	9/30/2011

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Moderate Allocation Fund | Moderate Allocation Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.12%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.17%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.86%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.15%

^[1]

1 Year

rr_ExpenseExampleYear01

$ 117

3 Years

rr_ExpenseExampleYear03

365

5 Years

rr_ExpenseExampleYear05

633

10 Years

rr_ExpenseExampleYear10

$ 1,398

2009

rr_AnnualReturn2009

20.58%

2010

rr_AnnualReturn2010

12.24%

2011

rr_AnnualReturn2011

0.65%

2012

rr_AnnualReturn2012

10.93%

2013

rr_AnnualReturn2013

14.11%

2014

rr_AnnualReturn2014

5.63%

2015

rr_AnnualReturn2015

(0.55%)

2016

rr_AnnualReturn2016

6.96%

2017

rr_AnnualReturn2017

14.00%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

11.68%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(9.29%)

1 Year

rr_AverageAnnualReturnYear01

14.00%

5 Years

rr_AverageAnnualReturnYear05

7.89%

Since Inception

rr_AverageAnnualReturnSinceInception

6.45%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Moderate Allocation Fund | Russell 3000® Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

21.13%

5 Years

rr_AverageAnnualReturnYear05

15.58%

Since Inception

rr_AverageAnnualReturnSinceInception

10.45%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Moderate Allocation Fund | Bloomberg Barclays Capital U.S. Aggregate Bond Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

3.54%

5 Years

rr_AverageAnnualReturnYear05

2.10%

Since Inception

rr_AverageAnnualReturnSinceInception

4.13%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Penn Series Moderately Conservative Allocation Fund

FUND SUMMARY:  MODERATELY CONSERVATIVE ALLOCATION FUND

Investment Objective

The investment objective of the Moderately Conservative Allocation Fund (the “Fund”) is to seek to achieve long-term capital growth and current income consistent with its asset allocation strategy.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Moderately Conservative Allocation Fund Moderately Conservative Allocation Fund
Investment Advisory Fees	0.12%
Distribution (12b-1) Fees	none
Other Expenses	0.18%
Acquired Fund Fees and Expenses	0.79%
Total Annual Fund Operating Expenses	1.09%	[1]

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Moderately Conservative Allocation Fund | Moderately Conservative Allocation Fund | USD ($)	111	347	601	1,329

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 15% of the average value of its portfolio.

Principal Investment Strategy

The Fund seeks to achieve its investment objective by using a “fund-of-funds” strategy. Accordingly, the Fund invests in a combination of other Penn Series Funds (each, an “underlying fund” and, collectively, the “underlying funds”) in accordance with its target asset allocations. These underlying funds invest their assets directly in equity, fixed income, money market and other securities in accordance with their own investment objectives and policies. The underlying funds are managed using both indexed and active management strategies.

The Fund has its own distinct target portfolio allocation and is designed to accommodate specific investment goals and risk tolerances. Through its investments in the underlying funds, the Fund’s target allocation is intended to allocate the Fund’s assets among various asset classes, such as equity securities, fixed income securities and money market securities. The portfolio of the Fund is more heavily allocated to bonds and cash investments, and reflects a moderately conservative approach.

In determining the asset allocation of the Fund, the Adviser will rely on the experience of its investment personnel and its evaluation of the overall financial markets, including, but not limited to, information about the economy, interest rates, and the long-term absolute and relative returns of various asset classes. Consideration will also be given to the investment styles of the managers of the underlying funds and their historic patterns of performance relative to their asset class and to other underlying funds. Periodic changes in allocations among the underlying funds will be based on information about the financial markets, changes within particular underlying funds, or the introduction of new Penn Series Funds that would, in the Adviser’s opinion, enhance the return potential of the Fund. These changes will be implemented as necessary, recognizing that these decisions tend to be long-term in nature, based on information about the financial markets and on the Fund’s investment objective.

The following chart shows the Fund’s target asset allocation among the various asset classes. The Adviser may permit modest deviations from the target asset allocations listed below. Accordingly, the Fund’s actual allocations may differ from this illustration.

Asset Class	Target Asset Allocation
Equity Funds	30% - 50%
Fixed Income and Money Market Funds	50% - 70%

The Adviser reserves the right to modify the Fund’s target asset allocations and to substitute other underlying funds and add additional underlying funds from time to time should circumstances warrant a change. The Adviser may periodically rebalance the Fund’s investments in the underlying funds to bring the Fund back within its target range.

Principal Risks

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Asset Allocation Risk.  The possibility that the Fund may underperform other funds with similar investment objectives due to the Fund’s allocation of assets to underlying funds investing in asset classes or market sectors that perform poorly relative to other asset categories.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Underlying Fund Investment Risk.  The possibility that the underperformance of an underlying fund may contribute to the underperformance of the Fund. The Fund’s performance and risks will be directly related to the performance and risks of the underlying funds in which it invests. In addition, the Fund indirectly pays a pro rata portion of the expenses incurred by the underlying funds, which also may lower the Fund’s performance.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by an underlying fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by an underlying fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by an underlying fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of an underlying fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that an underlying fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Adviser or Sub-Adviser of the underlying fund believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that an underlying fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that an underlying fund’s investments in securities of companies perceived to be “growth” companies may underperform when the underlying fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

High Yield Bond Risk.  The possibility that an underlying fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the underlying fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to the underlying fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Interest Rate Risk.  The possibility that the prices of an underlying fund’s fixed income investments will decline due to rising interest rates.

Investment Risk.  You may lose money by investing in the Money Market Fund. Although the Money Market Fund seeks to preserve the value of your investment at $1.00 per share, there is no guarantee that the Money Market Fund will be able to do so. An investment in the Money Market Fund is not insured or guaranteed by the FDIC or any other government agency. PMAM, the Fund’s sponsor, and its affiliates have no legal obligation to provide financial support to the Money Market Fund, and you should not expect that PMAM or its affiliates will provide financial support to the Money Market Fund at any time.

Large-Cap Securities Risk.  The possibility that an underlying fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of an underlying fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If an underlying fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Portfolio Turnover Risk.  The possibility that an underlying fund may frequently buy and sell portfolio securities, which may increase transaction costs to the underlying fund and cause the underlying fund’s performance to be less than you expect.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing an underlying fund to invest in fixed income securities with lower interest rates, which may adversely affect the underlying fund’s performance.

Small- and Mid-Cap Securities Risk.  The possibility that an underlying fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and an underlying fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by an underlying fund if it is not obligated to do because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause an underlying fund’s share price or yield to fall.

“Value” Investing Risk.  The possibility that an underlying fund’s investments in securities perceived to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which an underlying fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the underlying fund’s investment style shifts out of favor.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index and one additional index, the Russell 3000^® Index. The Russell 3000^® Index, in conjunction with the broad-based index, is used to track the broad range of allocations the Fund makes to the underlying funds. The foregoing indices, when considered together, may provide investors with a useful comparison of the Fund’s overall performance. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
8.62%	-5.34%
6/30/2009	9/30/2011

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Moderately Conservative Allocation Fund	1 Year	5 Years	Since Inception	Inception Date
Moderately Conservative Allocation Fund	9.99%	5.97%	5.39%	Aug. 25, 2008
Bloomberg Barclays Capital U.S. Aggregate Bond Index (reflects no deduction for fees, expenses or taxes)	3.54%	2.10%	4.13%	Aug. 25, 2008
Russell 3000® Index (reflects no deduction for fees, expenses or taxes)	21.13%	15.58%	10.45%	Aug. 25, 2008

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Moderately Conservative Allocation Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  MODERATELY CONSERVATIVE ALLOCATION FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Moderately Conservative Allocation Fund (the “Fund”) is to seek to achieve long-term capital growth and current income consistent with its asset allocation strategy.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 15% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

15.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund seeks to achieve its investment objective by using a “fund-of-funds” strategy. Accordingly, the Fund invests in a combination of other Penn Series Funds (each, an “underlying fund” and, collectively, the “underlying funds”) in accordance with its target asset allocations. These underlying funds invest their assets directly in equity, fixed income, money market and other securities in accordance with their own investment objectives and policies. The underlying funds are managed using both indexed and active management strategies.

The Fund has its own distinct target portfolio allocation and is designed to accommodate specific investment goals and risk tolerances. Through its investments in the underlying funds, the Fund’s target allocation is intended to allocate the Fund’s assets among various asset classes, such as equity securities, fixed income securities and money market securities. The portfolio of the Fund is more heavily allocated to bonds and cash investments, and reflects a moderately conservative approach.

In determining the asset allocation of the Fund, the Adviser will rely on the experience of its investment personnel and its evaluation of the overall financial markets, including, but not limited to, information about the economy, interest rates, and the long-term absolute and relative returns of various asset classes. Consideration will also be given to the investment styles of the managers of the underlying funds and their historic patterns of performance relative to their asset class and to other underlying funds. Periodic changes in allocations among the underlying funds will be based on information about the financial markets, changes within particular underlying funds, or the introduction of new Penn Series Funds that would, in the Adviser’s opinion, enhance the return potential of the Fund. These changes will be implemented as necessary, recognizing that these decisions tend to be long-term in nature, based on information about the financial markets and on the Fund’s investment objective.

The following chart shows the Fund’s target asset allocation among the various asset classes. The Adviser may permit modest deviations from the target asset allocations listed below. Accordingly, the Fund’s actual allocations may differ from this illustration.

Asset Class	Target Asset Allocation
Equity Funds	30% - 50%
Fixed Income and Money Market Funds	50% - 70%

The Adviser reserves the right to modify the Fund’s target asset allocations and to substitute other underlying funds and add additional underlying funds from time to time should circumstances warrant a change. The Adviser may periodically rebalance the Fund’s investments in the underlying funds to bring the Fund back within its target range.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Asset Allocation Risk.  The possibility that the Fund may underperform other funds with similar investment objectives due to the Fund’s allocation of assets to underlying funds investing in asset classes or market sectors that perform poorly relative to other asset categories.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Underlying Fund Investment Risk.  The possibility that the underperformance of an underlying fund may contribute to the underperformance of the Fund. The Fund’s performance and risks will be directly related to the performance and risks of the underlying funds in which it invests. In addition, the Fund indirectly pays a pro rata portion of the expenses incurred by the underlying funds, which also may lower the Fund’s performance.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by an underlying fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by an underlying fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by an underlying fund defaults on its payment obligations.

Currency Risk.  The possibility that the value of an underlying fund’s assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and restrictions or prohibitions on the repatriation of foreign currencies.

Derivatives Risk.  The possibility that an underlying fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Adviser or Sub-Adviser of the underlying fund believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that an underlying fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that an underlying fund’s investments in securities of companies perceived to be “growth” companies may underperform when the underlying fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

High Yield Bond Risk.  The possibility that an underlying fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the underlying fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to the underlying fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Interest Rate Risk.  The possibility that the prices of an underlying fund’s fixed income investments will decline due to rising interest rates.

Investment Risk.  You may lose money by investing in the Money Market Fund. Although the Money Market Fund seeks to preserve the value of your investment at $1.00 per share, there is no guarantee that the Money Market Fund will be able to do so. An investment in the Money Market Fund is not insured or guaranteed by the FDIC or any other government agency. PMAM, the Fund’s sponsor, and its affiliates have no legal obligation to provide financial support to the Money Market Fund, and you should not expect that PMAM or its affiliates will provide financial support to the Money Market Fund at any time.

Large-Cap Securities Risk.  The possibility that an underlying fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of an underlying fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If an underlying fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Portfolio Turnover Risk.  The possibility that an underlying fund may frequently buy and sell portfolio securities, which may increase transaction costs to the underlying fund and cause the underlying fund’s performance to be less than you expect.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing an underlying fund to invest in fixed income securities with lower interest rates, which may adversely affect the underlying fund’s performance.

Small- and Mid-Cap Securities Risk.  The possibility that an underlying fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and an underlying fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by an underlying fund if it is not obligated to do because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause an underlying fund’s share price or yield to fall.

“Value” Investing Risk.  The possibility that an underlying fund’s investments in securities perceived to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which an underlying fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the underlying fund’s investment style shifts out of favor.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index and one additional index, the Russell 3000^® Index. The Russell 3000^® Index, in conjunction with the broad-based index, is used to track the broad range of allocations the Fund makes to the underlying funds. The foregoing indices, when considered together, may provide investors with a useful comparison of the Fund’s overall performance. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index and one additional index, the Russell 3000^® Index.

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

The Russell 3000^® Index, in conjunction with the broad-based index, is used to track the broad range of allocations the Fund makes to the underlying funds. The foregoing indices, when considered together, may provide investors with a useful comparison of the Fund’s overall performance.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
8.62%	-5.34%
6/30/2009	9/30/2011

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Moderately Conservative Allocation Fund | Moderately Conservative Allocation Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.12%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.18%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.79%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.09%

^[1]

1 Year

rr_ExpenseExampleYear01

$ 111

3 Years

rr_ExpenseExampleYear03

347

5 Years

rr_ExpenseExampleYear05

601

10 Years

rr_ExpenseExampleYear10

$ 1,329

2009

rr_AnnualReturn2009

16.19%

2010

rr_AnnualReturn2010

9.32%

2011

rr_AnnualReturn2011

2.72%

2012

rr_AnnualReturn2012

8.30%

2013

rr_AnnualReturn2013

9.35%

2014

rr_AnnualReturn2014

5.01%

2015

rr_AnnualReturn2015

(0.22%)

2016

rr_AnnualReturn2016

6.03%

2017

rr_AnnualReturn2017

9.99%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

8.62%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(5.34%)

1 Year

rr_AverageAnnualReturnYear01

9.99%

5 Years

rr_AverageAnnualReturnYear05

5.97%

Since Inception

rr_AverageAnnualReturnSinceInception

5.39%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Moderately Conservative Allocation Fund | Bloomberg Barclays Capital U.S. Aggregate Bond Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

3.54%

5 Years

rr_AverageAnnualReturnYear05

2.10%

Since Inception

rr_AverageAnnualReturnSinceInception

4.13%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Moderately Conservative Allocation Fund | Russell 3000® Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

21.13%

5 Years

rr_AverageAnnualReturnYear05

15.58%

Since Inception

rr_AverageAnnualReturnSinceInception

10.45%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Penn Series Conservative Allocation Fund

FUND SUMMARY:  CONSERVATIVE ALLOCATION FUND

Investment Objective

The investment objective of the Conservative Allocation Fund (the “Fund”) is to seek to achieve long-term capital growth and current income consistent with its asset allocation strategy.

Fund Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Penn Series Conservative Allocation Fund Conservative Allocation Fund
Investment Advisory Fees	0.12%
Distribution (12b-1) Fees	none
Other Expenses	0.20%
Acquired Fund Fees and Expenses	0.73%
Total Annual Fund Operating Expenses	1.05%	[1]

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Expense Example	1 Year	3 Years	5 Years	10 Years
Penn Series Conservative Allocation Fund | Conservative Allocation Fund | USD ($)	107	334	579	1,283

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 23% of the average value of its portfolio.

Principal Investment Strategy

The Fund seeks to achieve its investment objective by using a “fund-of-funds” strategy. Accordingly, the Fund invests in a combination of other Penn Series Funds (each, an “underlying fund” and, collectively, the “underlying funds”) in accordance with its target asset allocations. These underlying funds invest their assets directly in equity, fixed income, money market and other securities in accordance with their own investment objectives and policies. The underlying funds are managed using both indexed and active management strategies.

The Fund has its own distinct target portfolio allocation and is designed to accommodate specific investment goals and risk tolerances. Through its investments in the underlying funds, the Fund’s target allocation is intended to allocate the Fund’s assets among various asset classes, such as equity securities, fixed income securities and money market securities. The portfolio of the Fund is more heavily allocated to bonds and cash investments, and reflects a conservative approach.

In determining the asset allocation of the Fund, the Adviser will rely on the experience of its investment personnel and its evaluation of the overall financial markets, including, but not limited to, information about the economy, interest rates, and the long-term absolute and relative returns of various asset classes. Consideration will also be given to the investment styles of the managers of the underlying funds and their historic patterns of performance relative to their asset class and to other underlying funds. Periodic changes in allocations among the underlying funds will be based on information about the financial markets, changes within particular underlying funds, or the introduction of new Penn Series Funds that would, in the Adviser’s opinion, enhance the return potential of the Fund. These changes will be implemented as necessary, recognizing that these decisions tend to be long-term in nature, based on information about the financial markets and on the Fund’s investment objective.

The following chart shows the Fund’s target asset allocation among the various asset classes. The Adviser may permit modest deviations from the target asset allocations listed below. Accordingly, the Fund’s actual allocations may differ from this illustration.

Asset Class	Target Asset Allocation
Equity Funds	20% - 40%
Fixed Income and Money Market Funds	60% - 80%

The Adviser reserves the right to modify the Fund’s target asset allocations and to substitute other underlying funds and add additional underlying funds from time to time should circumstances warrant a change. The Adviser may periodically rebalance the Fund’s investments in the underlying funds to bring the Fund back within its target range.

Principal Risks

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Asset Allocation Risk.  The possibility that the Fund may underperform other funds with similar investment objectives due to the Fund’s allocation of assets to underlying funds investing in asset classes or market sectors that perform poorly relative to other asset categories.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Underlying Fund Investment Risk.  The possibility that the underperformance of an underlying fund may contribute to the underperformance of the Fund. The Fund’s performance and risks will be directly related to the performance and risks of the underlying funds in which it invests. In addition, the Fund indirectly pays a pro rata portion of the expenses incurred by the underlying funds, which also may lower the Fund’s performance.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by an underlying fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by an underlying fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by an underlying fund defaults on its payment obligations.

Derivatives Risk.  The possibility that an underlying fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Adviser or Sub-Adviser of the underlying fund believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that an underlying fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that an underlying fund’s investments in securities of companies perceived to be “growth” companies may underperform when the underlying fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

High Yield Bond Risk.  The possibility that an underlying fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the underlying fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to the underlying fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Interest Rate Risk.  The possibility that the prices of an underlying fund’s fixed income investments will decline due to rising interest rates.

Investment Risk.  You may lose money by investing in the Money Market Fund. Although the Money Market Fund seeks to preserve the value of your investment at $1.00 per share, there is no guarantee that the Money Market Fund will be able to do so. An investment in the Money Market Fund is not insured or guaranteed by the FDIC or any other government agency. PMAM, the Fund’s sponsor, and its affiliates have no legal obligation to provide financial support to the Money Market Fund, and you should not expect that PMAM or its affiliates will provide financial support to the Money Market Fund at any time.

Large-Cap Securities Risk.  The possibility that an underlying fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of an underlying fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If an underlying fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Portfolio Turnover Risk.  The possibility that an underlying fund may frequently buy and sell portfolio securities, which may increase transaction costs to the underlying fund and cause the underlying fund’s performance to be less than you expect.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing an underlying fund to invest in fixed income securities with lower interest rates, which may adversely affect the underlying fund’s performance.

Small- and Mid-Cap Securities Risk.  The possibility that an underlying fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and an underlying fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by an underlying fund if it is not obligated to do because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause an underlying fund’s share price or yield to fall.

“Value” Investing Risk.  The possibility that an underlying fund’s investments in securities perceived to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which an underlying fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the underlying fund’s investment style shifts out of favor.

Performance Information

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index and one additional index, the Russell 3000^® Index. The Russell 3000^® Index, in conjunction with the broad-based index, is used to track the broad range of allocations the Fund makes to the underlying funds. The foregoing indices, when considered together, may provide investors with a useful comparison of the Fund’s overall performance. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Best Quarter	Worst Quarter
5.26%	-1.40%
6/30/2009	9/30/2015

Average Annual Total Return (for Periods Ended December 31, 2017)

Average Annual Total Returns - Penn Series Conservative Allocation Fund	1 Year	5 Years	Since Inception	Inception Date
Conservative Allocation Fund	6.38%	3.85%	4.16%	Aug. 25, 2008
Bloomberg Barclays Capital U.S. Aggregate Bond Index (reflects no deduction for fees, expenses or taxes)	3.54%	2.10%	4.13%	Aug. 25, 2008
Russell 3000® Index (reflects no deduction for fees, expenses or taxes)	21.13%	15.58%	10.45%	Aug. 25, 2008

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PENN SERIES FUNDS INC

Prospectus Date

rr_ProspectusDate

May 01, 2018

Penn Series Conservative Allocation Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

FUND SUMMARY:  CONSERVATIVE ALLOCATION FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The investment objective of the Conservative Allocation Fund (the “Fund”) is to seek to achieve long-term capital growth and current income consistent with its asset allocation strategy.

Expense [Heading]

rr_ExpenseHeading

Fund Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 23% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

23.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategy

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund seeks to achieve its investment objective by using a “fund-of-funds” strategy. Accordingly, the Fund invests in a combination of other Penn Series Funds (each, an “underlying fund” and, collectively, the “underlying funds”) in accordance with its target asset allocations. These underlying funds invest their assets directly in equity, fixed income, money market and other securities in accordance with their own investment objectives and policies. The underlying funds are managed using both indexed and active management strategies.

The Fund has its own distinct target portfolio allocation and is designed to accommodate specific investment goals and risk tolerances. Through its investments in the underlying funds, the Fund’s target allocation is intended to allocate the Fund’s assets among various asset classes, such as equity securities, fixed income securities and money market securities. The portfolio of the Fund is more heavily allocated to bonds and cash investments, and reflects a conservative approach.

In determining the asset allocation of the Fund, the Adviser will rely on the experience of its investment personnel and its evaluation of the overall financial markets, including, but not limited to, information about the economy, interest rates, and the long-term absolute and relative returns of various asset classes. Consideration will also be given to the investment styles of the managers of the underlying funds and their historic patterns of performance relative to their asset class and to other underlying funds. Periodic changes in allocations among the underlying funds will be based on information about the financial markets, changes within particular underlying funds, or the introduction of new Penn Series Funds that would, in the Adviser’s opinion, enhance the return potential of the Fund. These changes will be implemented as necessary, recognizing that these decisions tend to be long-term in nature, based on information about the financial markets and on the Fund’s investment objective.

The following chart shows the Fund’s target asset allocation among the various asset classes. The Adviser may permit modest deviations from the target asset allocations listed below. Accordingly, the Fund’s actual allocations may differ from this illustration.

Asset Class	Target Asset Allocation
Equity Funds	20% - 40%
Fixed Income and Money Market Funds	60% - 80%

The Adviser reserves the right to modify the Fund’s target asset allocations and to substitute other underlying funds and add additional underlying funds from time to time should circumstances warrant a change. The Adviser may periodically rebalance the Fund’s investments in the underlying funds to bring the Fund back within its target range.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Asset Allocation Risk.  The possibility that the Fund may underperform other funds with similar investment objectives due to the Fund’s allocation of assets to underlying funds investing in asset classes or market sectors that perform poorly relative to other asset categories.

Market Risk.  The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Underlying Fund Investment Risk.  The possibility that the underperformance of an underlying fund may contribute to the underperformance of the Fund. The Fund’s performance and risks will be directly related to the performance and risks of the underlying funds in which it invests. In addition, the Fund indirectly pays a pro rata portion of the expenses incurred by the underlying funds, which also may lower the Fund’s performance.

Corporate Debt Securities Risk.  The possibility that the issuer of a debt security held by an underlying fund is unable to meet its principal and interest payment obligations. The further possibility that corporate debt securities held by an underlying fund may experience increased price volatility due to such factors as market interest rates, market perception of the creditworthiness of the issuer and general market liquidity.

Credit Risk.  The possibility that an issuer of a debt security, or the counterparty to a derivatives contract, held by an underlying fund defaults on its payment obligations.

Derivatives Risk.  The possibility that an underlying fund’s use of derivatives, such as futures, options and swap agreements, may lead to losses, including those magnified by leverage, particularly when derivatives are used to enhance return rather than mitigate risk. Certain derivative instruments may be difficult to sell when the Adviser or Sub-Adviser of the underlying fund believes it would be appropriate to do so, difficult to value if the instrument becomes illiquid, or the other party to a derivative contract may be unwilling or unable to fulfill its contractual obligations.

Equity Securities Risk.  In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Foreign Investment Risk.  The possibility that an underlying fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

“Growth” Investing Risk.  The possibility that an underlying fund’s investments in securities of companies perceived to be “growth” companies may underperform when the underlying fund’s investment style shifts out of favor and may be more volatile than other securities because they are more sensitive to investor perceptions of the issuing company’s growth of earnings potential. Also, because growth companies usually invest a high portion of earnings in their businesses, growth stocks may lack the dividends of some value stocks that can cushion stock prices in a falling market.

High Yield Bond Risk.  The possibility that an underlying fund’s investment in debt securities rated below investment grade (commonly known as junk bonds) may adversely affect the underlying fund’s yield. Although these securities generally provide for higher yields than higher rated debt securities, the high degree of risk associated with these investments can result in substantial or total loss to the underlying fund. High yield securities are considered speculative and are subject to a greater risk of loss, greater sensitivity to interest rate changes, increased price volatility, valuation difficulties, and a potential lack of a liquid secondary or public market for the securities.

Interest Rate Risk.  The possibility that the prices of an underlying fund’s fixed income investments will decline due to rising interest rates.

Investment Risk.  You may lose money by investing in the Money Market Fund. Although the Money Market Fund seeks to preserve the value of your investment at $1.00 per share, there is no guarantee that the Money Market Fund will be able to do so. An investment in the Money Market Fund is not insured or guaranteed by the FDIC or any other government agency. PMAM, the Fund’s sponsor, and its affiliates have no legal obligation to provide financial support to the Money Market Fund, and you should not expect that PMAM or its affiliates will provide financial support to the Money Market Fund at any time.

Large-Cap Securities Risk.  The possibility that an underlying fund’s investments in larger companies may underperform relative to those of smaller companies. Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes and may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk.  The possibility that the market for certain of an underlying fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If an underlying fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Portfolio Turnover Risk.  The possibility that an underlying fund may frequently buy and sell portfolio securities, which may increase transaction costs to the underlying fund and cause the underlying fund’s performance to be less than you expect.

Prepayment and Extension Risk.  The possibility that the principal on a fixed income security may be paid off earlier or later than expected causing an underlying fund to invest in fixed income securities with lower interest rates, which may adversely affect the underlying fund’s performance.

Small- and Mid-Cap Securities Risk.  The possibility that an underlying fund’s investments in small- and mid-cap securities may be subject to greater risk and higher volatility than are customarily associated with investing in larger more established companies. Securities issued by small- and mid-sized companies, which can include start-up companies, tend to be more vulnerable than larger and more established companies to adverse business and economic developments. Such companies generally have narrower product lines, more limited financial resources and more limited markets for their stock as compared with larger companies. As a result, the value of such securities also may be more volatile than the securities of larger companies, and an underlying fund’s portfolio may experience difficulty in purchasing or selling such securities at the desired time and price or in the desired amount.

U.S. Government Securities Risk.  The possibility that the U.S. government will not provide financial assistance in support of securities issued by certain of its agencies and instrumentalities and held by an underlying fund if it is not obligated to do because such securities are not issued or guaranteed by the U.S. Treasury. A default by a U.S. government agency or instrumentality could cause an underlying fund’s share price or yield to fall.

“Value” Investing Risk.  The possibility that an underlying fund’s investments in securities perceived to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which an underlying fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the underlying fund’s investment style shifts out of favor.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below show the performance of the Fund both year-by-year and as an average over different periods of time. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index and one additional index, the Russell 3000^® Index. The Russell 3000^® Index, in conjunction with the broad-based index, is used to track the broad range of allocations the Fund makes to the underlying funds. The foregoing indices, when considered together, may provide investors with a useful comparison of the Fund’s overall performance. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index and one additional index, the Russell 3000^® Index.

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

The Russell 3000^® Index, in conjunction with the broad-based index, is used to track the broad range of allocations the Fund makes to the underlying funds. The foregoing indices, when considered together, may provide investors with a useful comparison of the Fund’s overall performance.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter	Worst Quarter
5.26%	-1.40%
6/30/2009	9/30/2015

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Return (for Periods Ended December 31, 2017)

Penn Series Conservative Allocation Fund | Conservative Allocation Fund

Risk/Return:

rr_RiskReturnAbstract

Investment Advisory Fees

rr_ManagementFeesOverAssets

0.12%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.20%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.73%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.05%

^[1]

1 Year

rr_ExpenseExampleYear01

$ 107

3 Years

rr_ExpenseExampleYear03

334

5 Years

rr_ExpenseExampleYear05

579

10 Years

rr_ExpenseExampleYear10

$ 1,283

2009

rr_AnnualReturn2009

10.80%

2010

rr_AnnualReturn2010

6.89%

2011

rr_AnnualReturn2011

3.92%

2012

rr_AnnualReturn2012

5.48%

2013

rr_AnnualReturn2013

4.43%

2014

rr_AnnualReturn2014

3.75%

2015

rr_AnnualReturn2015

0.08%

2016

rr_AnnualReturn2016

4.71%

2017

rr_AnnualReturn2017

6.38%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

5.26%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2015

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(1.40%)

1 Year

rr_AverageAnnualReturnYear01

6.38%

5 Years

rr_AverageAnnualReturnYear05

3.85%

Since Inception

rr_AverageAnnualReturnSinceInception

4.16%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Conservative Allocation Fund | Bloomberg Barclays Capital U.S. Aggregate Bond Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

3.54%

5 Years

rr_AverageAnnualReturnYear05

2.10%

Since Inception

rr_AverageAnnualReturnSinceInception

4.13%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

Penn Series Conservative Allocation Fund | Russell 3000® Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

21.13%

5 Years

rr_AverageAnnualReturnYear05

15.58%

Since Inception

rr_AverageAnnualReturnSinceInception

10.45%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 25, 2008

[1] The Total Annual Fund Operating Expenses in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	PENN SERIES FUNDS INC
Prospectus Date	rr_ProspectusDate	May 01, 2018
Document Creation Date	dei_DocumentCreationDate	Apr. 26, 2018