Label	Element	Value
DREYFUS FUND INC
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Summary
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The fund seeks long-term capital growth consistent with the preservation of capital.
Objective, Secondary [Text Block]	rr_ObjectiveSecondaryTextBlock	Current income is a secondary investment objective.
Expense [Heading]	rr_ExpenseHeading	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.
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 and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in 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 32.16% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	32.16%
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The 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 hold or 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 may 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	To pursue its goals, the fund primarily invests in common stocks issued by U.S. companies. The fund may invest up to 20% of its assets in foreign securities. In choosing stocks, the fund's portfolio managers focus on large-capitalization companies with strong positions in their industries and a catalyst that can trigger a price increase (such as a corporate restructuring or change in management). The portfolio managers use fundamental analysis to create a broadly diversified portfolio comprised of growth stocks, value stocks and stocks that exhibit characteristics of both investment styles. The portfolio managers attempt to measure a security's intrinsic value by analyzing "real" data (company financials, economic outlook, etc.) and other factors (management, industry conditions, competition, etc.) and select stocks based on value, growth and financial profile. The fund typically sells a security when the portfolio managers believe that there has been a negative change in the fundamental factors surrounding the company, the company has become fully valued, the company has lost favor in the current market or economic environment, or a more attractive opportunity has been identified.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the fund is not a bank deposit. It is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency. It is not a complete investment program. The fund's share price fluctuates, sometimes dramatically, which means you could lose money. · Risks of stock investing. Stocks generally fluctuate more in value than bonds and may decline significantly over short time periods. There is the chance that stock prices overall will decline because stock markets tend to move in cycles, with periods of rising prices and falling prices. The market value of a stock may decline due to general market conditions or because of factors that affect the particular company or the company's industry. · Growth and value stock risk. By investing in a mix of growth and value companies, the fund assumes the risks of both. Investors often expect growth companies to increase their earnings at a certain rate. If these expectations are not met, investors can punish the stocks inordinately, even if earnings do increase. In addition, growth stocks may lack the dividend yield that may cushion stock prices in market downturns. Value stocks involve the risk that they may never reach their expected full market value, either because the market fails to recognize the stock's intrinsic worth or the expected value was misgauged. · Large-cap stock risk. To the extent the fund invests in large capitalization stocks, the fund may underperform funds that invest primarily in the stocks of lower quality, smaller capitalization companies during periods when the stocks of such companies are in favor. · Market sector risk. The fund may significantly overweight or underweight certain companies, industries or market sectors, which may cause the fund's performance to be more or less sensitive to developments affecting those companies, industries or sectors. · Foreign investment risk. To the extent the fund invests in foreign securities, the fund's performance will be influenced by political, social and economic factors affecting investments in foreign issuers. Special risks associated with investments in foreign issuers include exposure to currency fluctuations, less liquidity, less developed or less efficient trading markets, lack of comprehensive company information, political and economic instability and differing auditing and legal standards. Investments denominated in foreign currencies are subject to the risk that such currencies will decline in value relative to the U.S. dollar and affect the value of these investments held by the fund. · Management risk. The investment process used by the fund's portfolio managers could fail to achieve the fund's investment goal and cause your fund investment to lose value.
Risk Lose Money [Text]	rr_RiskLoseMoney	The fund's share price fluctuates, sometimes dramatically, which means you could lose money.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	An investment in the fund is not a bank deposit. It 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
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the performance of the fund's shares from year to year. The table compares the average annual total returns of the fund's shares to those of a broad measure of market performance. The fund's past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. More recent performance information may be available at www.dreyfus.com.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The following bar chart and table provide some indication of the risks of investing in the fund.
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	www.dreyfus.com
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The fund's past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Year-by-Year Total Returns as of 12/31 each year (%)
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter Q3, 2009: 18.17% Worst Quarter Q3, 2011: -17.71%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	18.17%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2011
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(17.71%)
Index No Deduction for Fees, Expenses, Taxes [Text]	rr_IndexNoDeductionForFeesExpensesTaxes	reflects no deductions for fees, expenses or taxes
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	Actual after-tax returns depend on the investor's tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through U.S. tax-deferred arrangements such as 401(k) plans or individual retirement accounts.
Performance Table Explanation after Tax Higher	rr_PerformanceTableExplanationAfterTaxHigher	Returns after taxes on distributions and sale of fund shares may be higher than returns before taxes or returns after taxes on distributions due to an assumed tax benefit from losses on a sale of the fund's shares at the end of the period.
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect the impact of state and local taxes. Actual after-tax returns depend on the investor's tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through U.S. tax-deferred arrangements such as 401(k) plans or individual retirement accounts. Returns after taxes on distributions and sale of fund shares may be higher than returns before taxes or returns after taxes on distributions due to an assumed tax benefit from losses on a sale of the fund's shares at the end of the period.
Caption	rr_AverageAnnualReturnCaption	Average Annual Total Returns (as of 12/31/18)
DREYFUS FUND INC \| S&P 500® Index reflects no deductions for fees, expenses or taxes
Risk/Return:	rr_RiskReturnAbstract
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	(4.38%)
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	8.49%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	13.11%
DREYFUS FUND INC \| DREYFUS FUND INC
Risk/Return:	rr_RiskReturnAbstract
Management fees	rr_ManagementFeesOverAssets	0.65%
Other expenses	rr_OtherExpensesOverAssets	0.06%
Total annual fund operating expenses	rr_ExpensesOverAssets	0.71%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	$ 73
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	227
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	395
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	883
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	73
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	227
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	395
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 883
Annual Return 2009	rr_AnnualReturn2009	28.75%
Annual Return 2010	rr_AnnualReturn2010	16.30%
Annual Return 2011	rr_AnnualReturn2011	(5.05%)
Annual Return 2012	rr_AnnualReturn2012	17.58%
Annual Return 2013	rr_AnnualReturn2013	32.33%
Annual Return 2014	rr_AnnualReturn2014	9.47%
Annual Return 2015	rr_AnnualReturn2015	2.08%
Annual Return 2016	rr_AnnualReturn2016	7.23%
Annual Return 2017	rr_AnnualReturn2017	20.12%
Annual Return 2018	rr_AnnualReturn2018	(1.20%)
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	(1.20%)
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	7.30%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	12.14%
DREYFUS FUND INC \| DREYFUS FUND INC \| After Taxes on Distributions
Risk/Return:	rr_RiskReturnAbstract
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	(3.16%)
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	4.90%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	10.57%
DREYFUS FUND INC \| DREYFUS FUND INC \| After Taxes on Distributions and Sale of Fund Shares
Risk/Return:	rr_RiskReturnAbstract
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	0.70%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	5.45%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	9.92%

If the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form
-Number N-1A
-Chapter A
-Section 4
-Subsection b
-Paragraph 2
-Subparagraph instructions
-Clause 3
-Exhibit a