Label

Element

Value

Risk/Return:

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Registrant Name

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PENN SERIES FUNDS INC

Prospectus Date

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May 01, 2015

Penn Series Mid Cap Growth Fund

Risk/Return:

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Risk/Return [Heading]

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FUND SUMMARY:  MID CAP GROWTH FUND

Objective [Heading]

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Investment Objective

Objective, Primary [Text Block]

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The investment objective of the Mid Cap Growth Fund (the “Fund”) is to maximize capital appreciation.

Expense [Heading]

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Fund Fees and Expenses

Expense Narrative [Text Block]

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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]

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

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover [Text Block]

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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 140% of the average value of its portfolio.

Portfolio Turnover, Rate

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140.00%

Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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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. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

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Principal Investment Strategy

Strategy Narrative [Text Block]

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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, 2015, this range was between $212.69 million and $37.66 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. The Fund will invest in equity securities of companies that the Sub-Adviser believes have strong earnings growth potential and that are diversified across economic sectors. The Fund's exposure is generally limited to 5% of assets in any single issuer, subject to exceptions for the most heavily-weighted securities in the Russell Midcap^® Growth Index.

Risk [Heading]

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Principal Risks of Investing

Risk Narrative [Text Block]

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“Growth” Investing Risk.  The possibility that the Fund’s investments in securities of companies perceived to be “growth” companies may underperform when value investing is in 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.

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.

Bar Chart and Performance Table [Heading]

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Performance Information

Performance Narrative [Text Block]

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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. They represent the performance of the Fund’s previous managers for the period prior to May 1, 2014. Since May 1, 2014, Ivy Investment Management 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]

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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. They represent the performance of the Fund’s previous managers for the period prior to May 1, 2014. Since May 1, 2014, Ivy Investment Management 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.

Performance Past Does Not Indicate Future [Text]

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

Bar Chart Does Not Reflect Sales Loads [Text]

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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]

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Best Quarter	Worst Quarter
22.84%	-28.78%
9/30/2009	12/31/2008

Performance Table Heading

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Average Annual Total Return (for Periods Ended December 31, 2014)

Penn Series Mid Cap Growth Fund | Mid Cap Growth Fund

Risk/Return:

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Investment Advisory Fees

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0.70%

Distribution (12b-1) Fees

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none

Other Expenses

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0.27%

Total Annual Fund Operating Expenses

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0.97%

1 Year

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99

3 Years

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309

5 Years

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536

10 Years

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1,190

2005

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12.48%

2006

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6.81%

2007

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25.15%

2008

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(48.87%)

2009

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47.79%

2010

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26.84%

2011

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(7.78%)

2012

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6.08%

2013

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36.72%

2014

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9.49%

Highest Quarterly Return, Label

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Best Quarter

Highest Quarterly Return, Date

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Sep. 30, 2009

Highest Quarterly Return

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22.84%

Lowest Quarterly Return, Label

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Worst Quarter

Lowest Quarterly Return, Date

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Dec. 31, 2008

Lowest Quarterly Return

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(28.78%)

1 Year

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9.49%

5 Years

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13.19%

10 Years

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7.76%

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

Risk/Return:

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1 Year

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11.90%

5 Years

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16.94%

10 Years

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9.43%