Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	PENN SERIES FUNDS INC
Prospectus Date	rr_ProspectusDate	May 01, 2012
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 returns.
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. The information in this table and the Example that follows does not reflect charges and fees deducted under your insurance contract. These charges and fees will increase expenses.
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 160% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	160.00%
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 assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The costs would be the same whether you stayed in the Fund or sold your shares at the end of each period. 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 conditions, the Fund invests at least 80% of its net assets in securities of small and medium capitalization companies. This policy may be changed without the vote of shareholders but shareholders will be given 60 days’ advance notice of any change. For purposes of this policy, small and medium capitalization companies have market capitalizations that fall within the market capitalization range of companies in the Russell 2500 Growth Index at the time of purchase (as of March 31, 2012, this range was between $27 million and $11.6 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 Sub-Adviser’s strategy seeks superior, long-term returns by identifying growth companies at an early or transitional stage of development, before the market discovers their potential. The Sub-Adviser employs a bottom-up investment approach applying original idea generation, fundamental research, and security analysis emphasizing growth companies at attractive valuations. The Sub-Adviser’s approach emphasizes the predictability of earnings in order to seek to deliver superior investment results with controlled risk. The Sub-Adviser’s process is designed to identify small to mid cap companies with earnings growing at greater than 20% on average. The Sub-Adviser constructs the Fund’s portfolio using a two-tier process in order to concentrate holdings in the Sub-Adviser’s “best ideas.” The Fund’s top tier is typically composed of 20-30 stocks typically comprising 40% to 50% of the Fund’s total assets. These top tier stocks have proven their ability over time to deliver earnings in line with, or better than, the Sub-Adviser’s expectations. The Fund’s primary tier is typically composed of 40-70 stocks typically comprising 50%-60% of the Fund’s total assets. These smaller positions’ potential and other characteristics have met the Sub-Adviser’s initial due diligence criteria of accelerating earnings growth, strong business fundamentals, and attractive valuations versus peer groups. Over time, stocks in the primary tier either join the top tier or are eliminated from the Fund’s portfolio. The primary tier allows the Sub-Adviser to make investments in promising opportunities, while recognizing the need for confirmation of the research and seasoning. The Sub-Adviser believes that the two-tiered approach allows for concentration in the Sub-Adviser’s best ideas, while at the same time maintaining prudent diversification. The Sub-Adviser seeks to have the Fund broadly diversified across industry groups. The Sub-Adviser will sell a security when it reaches its target price and when a more attractive investment opportunity is available and the Fund is fully invested. If a security’s price falls 20% below cost (after adjustment for major market declines), the Sub-Adviser will review the security and, after such review, the security may be sold if the Sub-Adviser concludes that deteriorating fundamentals warrants the sale.
Risk [Heading]	rr_RiskHeading	Principal Risks of Investing
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Market Risk. Equity markets rise and fall daily. As with any investment whose performance is tied to these markets, the value of your investment in the Fund will fluctuate, which means that you could lose money. Equity Risk. The prices of equity securities rise and fall daily. These price movements may result from factors affecting individual companies, industries or the securities market as a whole. In addition, equity markets tend to move in cycles which may cause stock prices to fall over short or extended periods of time. Small- and Mid-Cap Risk. Historically, small- and mid-cap stocks have been riskier than large-cap stocks. 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- and mid-cap companies themselves may be more vulnerable to adverse business or economic events than larger, more established companies. Micro-Cap Risk. Micro-cap companies are followed by relatively few securities analysts and there tends to be less information about them. Their securities generally have limited trading volumes and are subject to even more abrupt, erratic price movements than small cap companies. “Growth” Investing Risk. Growth stocks can be volatile for several reasons. The prices of growth stocks are based largely on projections of the issuer’s future earnings and revenues. If a company’s earnings or revenues fall short of expectations, its stock price may fall dramatically. Growth stocks may be more expensive relative to their earnings or assets compared to value or other stocks. Liquidity Risk. A particular investment may be difficult to purchase or sell. The Fund may be unable to sell illiquid securities at an advantageous time or price. 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 any investment whose performance is tied to these markets, the value of your investment in the Fund will fluctuate, which means that you 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 insurance contract. If it did, returns would be lower.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	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.
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 insurance contract. If it did, returns would be lower.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter                                   Worst Quarter 21.48%                                            -19.83% 06/30/09                                            09/30/11
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Return (for Periods Ended December 31, 2011)
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	0.38%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.14%
Less Fee Waivers	rr_FeeWaiverOrReimbursementOverAssets	(0.08%)	[1]
Total Annual Fund Operating Expenses	rr_NetExpensesOverAssets	1.06%	[2]
1 Year	rr_ExpenseExampleYear01	108
3 Years	rr_ExpenseExampleYear03	337
5 Years	rr_ExpenseExampleYear05	585
10 Years	rr_ExpenseExampleYear10	1,294
2009	rr_AnnualReturn2009	54.15%
2010	rr_AnnualReturn2010	24.85%
2011	rr_AnnualReturn2011	(4.72%)
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	(4.72%)
Since Inception	rr_AverageAnnualReturnSinceInception	5.38%
Inception Date	rr_AverageAnnualReturnInceptionDate	Aug. 25, 2008
PENN SERIES SMID CAP GROWTH FUND | Russell 2500 Growth Index (reflects no deduction for expenses and taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(1.57%)
Since Inception	rr_AverageAnnualReturnSinceInception	3.58%
Inception Date	rr_AverageAnnualReturnInceptionDate	Aug. 25, 2008

[1] Penn Mutual and the Adviser have contractually agreed under an expense limitation agreement with the Company to waive a portion of their fees and/or reimburse expenses to the extent necessary to keep total annual operating expenses of the Fund from exceeding 1.05% of average daily net assets. This agreement is limited to the Fund's direct operating expenses and, therefore, does not apply to "Acquired Fund Fees and Expenses." Further, this agreement is expected to continue for the life of the Fund and it may only be terminated with the approval of the Company's Board of Directors.

[2] After Fee Waivers