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DREYFUS THIRD CENTURY 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 to provide capital growth,
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock

with current income as a secondary goal.
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. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the fund or certain other funds in the Dreyfus Family of Funds. More information about these and other discounts is available from your financial professional and in the Shareholder Guide section beginning on page 8 of the prospectus and in the How to Buy Shares section and the Additional Information About How to Buy Shares section beginning on page II-1 and page III-1, respectively, of the fund's Statement of Additional Information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
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 61.45% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 61.45%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the fund or certain other funds in the Dreyfus Family of Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
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 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:
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption You would pay the following expenses if you did not redeem your shares:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

To pursue its goals, the fund, under normal circumstances, invests at least 80% of its net assets in the common stocks of companies that, in the opinion of the fund's management, meet traditional investment standards and conduct their business in a manner that contributes to the enhancement of the quality of life in America.


The fund's investment strategy combines a disciplined investment process that consists of computer modeling techniques, fundamental analysis and risk management with a social investment process. In selecting stocks, the portfolio managers begin by using computer models to identify and rank stocks within an industry or sector, based on several characteristics, including value, growth and financial profile.


Next, based on fundamental analysis, the portfolio managers designate the most attractive of the higher ranked securities as potential purchase candidates, drawing on a variety of sources, including company management and internal as well as Wall Street research.


The portfolio managers then evaluate each stock considered to be a potential purchase candidate, by industry or sector, to determine whether the company enhances the quality of life in America by considering its record in the areas of protection and improvement of the environment and the proper use of our natural resources, occupational health and safety, consumer protection and product purity and equal employment opportunity.


The portfolio managers then further examine the companies determined to be eligible for purchase, by industry or sector, and select investments from those companies the portfolio managers consider to be the most attractive based on financial considerations.


The fund normally focuses on large-cap growth stocks but also may invest in value-oriented stocks, mid-cap stocks and small-cap stocks.
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.


· Social investment risk. Socially responsible investment criteria may limit the number of investment opportunities available to the fund, and as a result, at times the fund's returns may be lower than those funds that are not subject to such special investment considerations. If the portfolio managers determine that a company in the fund's portfolio fails to meet the fund's social criteria, the company's stock will be sold as soon as reasonably possible, consistent with the best interests of the fund.


· 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.


· Small and midsize company risk. Small and midsize companies carry additional risks because the operating histories of these companies tend to be more limited, their earnings and revenues less predictable (and some companies may be experiencing significant losses), and their share prices more volatile than those of larger, more established companies. These companies may have limited product lines, markets or financial resources, or may depend on a limited management group. Other investments are made in anticipation of future products, services or events whose delay or cancellation could cause the stock price to drop. The shares of smaller companies tend to trade less frequently than those of larger, more established companies, which can adversely affect the pricing of these securities and the fund's ability to sell these securities. Some of the fund's investments will rise and fall based on investor perception rather than economic factors.


· Growth stock risk. 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 stock risk. 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. They also may decline in price even though in theory they are already undervalued.
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 Class Z 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. Sales charges, if any, are not reflected in the bar chart, and if those charges were included, returns would have been less than those shown. 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 (%) Class Z
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads Sales charges, if any, are not reflected in the bar chart, and if those charges were included, returns would have been less than those shown.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter
Q2, 2009: 17.10%


Worst Quarter
Q4, 2008: -21.30%


The year-to-date total return of the fund's Class Z shares as of June 30, 2016 was 1.25%.

Year to Date Return, Label rr_YearToDateReturnLabel The year-to-date total return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2016
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 1.25%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 17.10%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (21.30%)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes reflects no deduction 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 One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax performance is shown only for Class Z shares. After tax performance of the fund's other share classes will vary.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax performance is shown only for Class Z shares. After tax performance of the fund's other share classes will vary. 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.


For the fund's Class Y shares, periods prior to the inception date reflect the performance of the fund's Class Z shares. Such performance figures have not been adjusted to reflect applicable class fees and expenses. Each share class is invested in the same portfolio of securities, and the annual returns would have differed only to the extent that the classes do not have the same expenses.

Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (as of 12/31/15)
DREYFUS THIRD CENTURY FUND INC | S&P 500® Index reflects no deduction for fees, expenses or taxes  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 1.39%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 12.55%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 7.30%
DREYFUS THIRD CENTURY FUND INC | Class A  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum deferred sales charge (load) (as a percentage of lower of purchase or sale price) rr_MaximumDeferredSalesChargeOverOther none [1]
Management fees rr_ManagementFeesOverAssets 0.75%
Distribution (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses (including shareholder services fees) rr_OtherExpensesOverAssets 0.48%
Total annual fund operating expenses rr_ExpensesOverAssets 1.23%
Expenses Deferred Charges [Text Block] rr_ExpensesDeferredChargesTextBlock Class A shares bought without an initial sales charge as part of an investment of $1 million or more may be charged a deferred sales charge of 1.00% if redeemed within one year.
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 693
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 943
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,212
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,978
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 693
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 943
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,212
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,978
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (8.91%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 8.98%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 5.96%
DREYFUS THIRD CENTURY FUND INC | Class C  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of lower of purchase or sale price) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management fees rr_ManagementFeesOverAssets 0.75%
Distribution (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.75%
Other expenses (including shareholder services fees) rr_OtherExpensesOverAssets 0.48%
Total annual fund operating expenses rr_ExpensesOverAssets 1.98%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 301
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 621
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,068
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,306
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 201
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 621
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,068
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,306
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (5.04%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 9.47%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 5.80%
DREYFUS THIRD CENTURY FUND INC | Class I  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of lower of purchase or sale price) rr_MaximumDeferredSalesChargeOverOther none
Management fees rr_ManagementFeesOverAssets 0.75%
Distribution (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses (including shareholder services fees) rr_OtherExpensesOverAssets 0.16%
Total annual fund operating expenses rr_ExpensesOverAssets 0.91%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 93
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 290
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 504
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,120
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 93
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 290
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 504
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,120
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (3.10%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 10.67%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 7.04%
DREYFUS THIRD CENTURY FUND INC | Class Y  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of lower of purchase or sale price) rr_MaximumDeferredSalesChargeOverOther none
Management fees rr_ManagementFeesOverAssets 0.75%
Distribution (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses (including shareholder services fees) rr_OtherExpensesOverAssets 0.13% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.88%
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Other expenses for Class Y are estimated amounts for the current fiscal year based on the Other expenses for Class I.
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 90
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 281
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 488
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,084
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 90
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 281
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 488
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,084
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (3.20%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 10.55%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 6.86%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Sep. 30, 2016
DREYFUS THIRD CENTURY FUND INC | Class Z  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of lower of purchase or sale price) rr_MaximumDeferredSalesChargeOverOther none
Management fees rr_ManagementFeesOverAssets 0.75%
Distribution (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses (including shareholder services fees) rr_OtherExpensesOverAssets 0.28%
Total annual fund operating expenses rr_ExpensesOverAssets 1.03%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 105
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 328
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 569
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,259
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 105
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 328
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 569
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,259
Annual Return 2006 rr_AnnualReturn2006 9.01%
Annual Return 2007 rr_AnnualReturn2007 7.56%
Annual Return 2008 rr_AnnualReturn2008 (34.30%)
Annual Return 2009 rr_AnnualReturn2009 33.30%
Annual Return 2010 rr_AnnualReturn2010 14.49%
Annual Return 2011 rr_AnnualReturn2011 0.69%
Annual Return 2012 rr_AnnualReturn2012 11.66%
Annual Return 2013 rr_AnnualReturn2013 34.09%
Annual Return 2014 rr_AnnualReturn2014 13.15%
Annual Return 2015 rr_AnnualReturn2015 (3.20%)
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (3.20%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 10.55%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 6.86%
DREYFUS THIRD CENTURY FUND INC | Class Z | After Taxes on Distributions  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (6.21%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 8.98%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 6.06%
DREYFUS THIRD CENTURY FUND INC | Class Z | After Taxes on Distributions and Sale of Fund Shares  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 0.71%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 8.39%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 5.55%
[1] Class A shares bought without an initial sales charge as part of an investment of $1 million or more may be charged a deferred sales charge of 1.00% if redeemed within one year.
[2] Other expenses for Class Y are estimated amounts for the current fiscal year based on the Other expenses for Class I.