Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	PARNASSUS FUNDS
Prospectus Date	rr_ProspectusDate	May 01, 2015
Parnassus Mid Cap Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Parnassus Mid Cap Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Parnassus Mid Cap Fund has the overall investment objective of capital appreciation.
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 Parnassus Mid Cap 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)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	May 1, 2017
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Parnassus Mid Cap 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 21.6% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	21.60%
Expense Footnotes [Text Block]	rr_ExpenseFootnotesTextBlock	For additional information about the Parnassus Mid Cap Fund’s expenses, please see “Financial Highlights” in the prospectus.
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 Parnassus Mid Cap 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 expenses are equal to the net annual fund operating expenses for the first two years and the total annual fund operating expenses for the remaining years. Although your actual costs may be higher or lower, under these assumptions, your costs would be:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Parnassus Mid Cap Fund normally invests at least 80% of its net assets in mid-sized companies. The Fund considers a mid-sized company to be one that has a market capitalization between that of the smallest and largest constituents of the Russell Midcap Index (which was between $211 million and $39 billion as of March 31, 2015) measured at the time of purchase. The Russell Midcap Index includes approximately 800 of the smallest companies in the Russell 1000 Index. The Fund will not automatically sell or cease to purchase stock of a company it already owns just because the company’s market capitalization grows or falls outside the ranges of the Russell Midcap Index, which are subject to change. The Fund may normally invest up to 20% of its net assets in smaller- and larger-capitalization companies. The Fund invests mainly in domestic stocks of companies that are financially sound and have good prospects for the future, and may invest up to 20% of its assets in foreign securities of similar companies. The Fund may purchase foreign securities directly on foreign markets. Using a value-oriented investment process, the Fund seeks to invest in equity securities that have the potential for long-term capital appreciation. To determine a company’s prospects, the Adviser reviews the company’s income statement, cash flow statement and balance sheet, and analyzes the company’s sustainable strategic advantage and management team. Upon initial investment, a company’s stock must be trading below its intrinsic value, which means that the Adviser seeks to purchase stock trading at a discount to the Adviser’s assessment of the company’s estimated value. The Adviser also takes environmental, social and governance factors into account in making investment decisions. The Fund will sell a security if the Adviser believes a company’s fundamentals will deteriorate or if it believes a company’s stock has little potential for appreciation.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	All investments involve risk, and investing in the Parnassus Mid Cap Fund is no exception. You could lose money investing in the Fund. The likelihood of loss may be greater if you invest for a shorter period of time. The Fund is intended for investors who can accept that there will be fluctuations in value. Investments in the Fund are not deposits, endorsements or guarantees of any bank and are not insured by the Federal Deposit Insurance Corporation or any other government agency. The Fund’s principal risks include the following: Stock Market Risk. The Fund invests in common stocks, whose prices fluctuate in response to the fortunes of individual companies and in response to general market and economic conditions both in the U.S. and abroad. The Fund’s holdings can vary significantly from broad stock market indices. Small- and Mid-Capitalization Company Risk. The Fund invests primarily in mid-capitalization companies and may also invest in small-capitalization companies, both of which can be particularly sensitive to changing economic conditions since they do not have the financial resources or the well-established businesses of large-capitalization companies. Relative to the stocks of large-capitalization companies, the stocks of small- and mid-capitalization companies are often thinly traded, and purchases and sales may result in higher transaction costs. Also, smaller capitalization companies tend to perform poorly during times of economic stress. Management Risk. The Adviser may be wrong in its assessment of a company’s value and/or the stocks the Fund holds may not reach what the Adviser believes are their full values. From time to time, “value” investing falls out of favor with investors, and during those periods the Fund’s relative performance may suffer. Foreign Securities Risk. The Fund may invest up to 20% of its assets in foreign securities. Foreign markets can be more volatile than the U.S. market due to increased risks of adverse issuer, political, regulatory, market or economic developments and can perform differently from the U.S. market.
Risk Lose Money [Text]	rr_RiskLoseMoney	You could lose money investing in the Fund.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	Investments in the Fund are not deposits, endorsements or guarantees of any bank and are not insured by the Federal Deposit Insurance Corporation 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 that follow contain information that allows you to evaluate the Parnassus Mid Cap Fund’s performance using several measures, such as yearly changes in performance, best and worst quarterly returns, and average annual total returns before and after taxes compared to a broad measure of market performance. The bar chart shows the performance of the Fund’s Investor Shares, and performance of the Fund’s Institutional Shares will differ from those shown to the extent that the classes of shares do not have the same expenses or inception date. How the Fund performed in the past (before and after taxes) is not necessarily an indication of how it will perform in the future. Updated performance information is available on the Fund’s website, www.parnassus.com, or by calling toll-free at (800) 999-3505.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and table that follow contain information that allows you to evaluate the Parnassus Mid Cap Fund’s performance using several measures, such as yearly changes in performance, best and worst quarterly returns, and average annual total returns before and after taxes compared to a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	(800) 999-3505
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	www.parnassus.com
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	How the Fund performed in the past (before and after taxes) is not necessarily an indication of how it will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the period shown in the bar chart, the highest return for a quarter was 18.3% (quarter ended June 30, 2009), and the lowest return for a quarter was a loss of 22.0% (quarter ended December 31, 2008).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (%) (all periods ended December 31, 2014)
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	The 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	After-tax returns are not relevant to investors who hold their Fund shares through 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 returns are shown for Investor Shares only. After-tax returns for Institutional Shares will vary.
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	Below is a table comparing the performance of the Parnassus Mid Cap Fund’s two share classes with that of the Russell Midcap Index and the Lipper Mid-Cap Core Average. Figures are average annual returns for one- and five-year periods ended December 31, 2014 and since inception (April 29, 2005). The table is intended to demonstrate the risk of investing in the Fund by showing how the Fund’s average annual total returns, before and after taxes, compare with a broad measure of market performance, the Russell Midcap Index, and a group of similar mutual funds, the Lipper Mid-Cap Core Average, and also how the Fund’s performance varies from year to year.
Performance Table Closing [Text Block]	rr_PerformanceTableClosingTextBlock	The 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 an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Investor Shares only. After-tax returns for Institutional Shares will vary. Parnassus Mid Cap Fund—Institutional Shares were incepted on April 30, 2015. Performance shown prior to the inception of the Institutional Shares reflects the performance of the Parnassus Mid Cap Fund—Investor Shares and includes expenses that are not applicable to and are higher than those of the Institutional Shares.
Parnassus Mid Cap Fund | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.74%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Service Fees	rr_Component1OtherExpensesOverAssets	0.15%
All remaining other expenses	rr_Component2OtherExpensesOverAssets	0.20%
Other Expenses	rr_OtherExpensesOverAssets	0.35%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.09%
Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	0.10%
Total Annual Fund Operating Expenses After Expense Reimbursement	rr_NetExpensesOverAssets	0.99%	[1]
1 Year	rr_ExpenseExampleYear01	101
3 Years	rr_ExpenseExampleYear03	326
5 Years	rr_ExpenseExampleYear05	581
10 Years	rr_ExpenseExampleYear10	1,310
2006	rr_AnnualReturn2006	15.78%
2007	rr_AnnualReturn2007	1.81%
2008	rr_AnnualReturn2008	(29.38%)
2009	rr_AnnualReturn2009	36.26%
2010	rr_AnnualReturn2010	18.70%
2011	rr_AnnualReturn2011	3.33%
2012	rr_AnnualReturn2012	18.58%
2013	rr_AnnualReturn2013	28.27%
2014	rr_AnnualReturn2014	11.24%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	18.30%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(22.00%)
One Year	rr_AverageAnnualReturnYear01	11.24%
Five Years	rr_AverageAnnualReturnYear05	15.72%
Since Inception	rr_AverageAnnualReturnSinceInception	9.62%
Inception Date	rr_AverageAnnualReturnInceptionDate	Apr. 29, 2005
Parnassus Mid Cap Fund | Institutional Shares
Risk/Return:	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.74%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Service Fees	rr_Component1OtherExpensesOverAssets	none
All remaining other expenses	rr_Component2OtherExpensesOverAssets	0.20%
Other Expenses	rr_OtherExpensesOverAssets	0.20%	[2]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.94%
Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	0.09%
Total Annual Fund Operating Expenses After Expense Reimbursement	rr_NetExpensesOverAssets	0.85%	[1]
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other expenses have been estimated based on actual expenses of the Investor Shares during the fiscal year ended December 31, 2014.
1 Year	rr_ExpenseExampleYear01	87
3 Years	rr_ExpenseExampleYear03	281
5 Years	rr_ExpenseExampleYear05	502
10 Years	rr_ExpenseExampleYear10	1,137
One Year	rr_AverageAnnualReturnYear01	11.24%
Five Years	rr_AverageAnnualReturnYear05	15.72%
Since Inception	rr_AverageAnnualReturnSinceInception	9.62%
Inception Date	rr_AverageAnnualReturnInceptionDate	Apr. 30, 2015
Parnassus Mid Cap Fund | Return after Taxes on Distributions | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
One Year	rr_AverageAnnualReturnYear01	10.74%
Five Years	rr_AverageAnnualReturnYear05	14.89%
Since Inception	rr_AverageAnnualReturnSinceInception	8.99%
Inception Date	rr_AverageAnnualReturnInceptionDate	Apr. 29, 2005
Parnassus Mid Cap Fund | Return after Taxes on Distributions and Sale of Fund Shares | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
One Year	rr_AverageAnnualReturnYear01	6.77%
Five Years	rr_AverageAnnualReturnYear05	12.70%
Since Inception	rr_AverageAnnualReturnSinceInception	7.80%
Inception Date	rr_AverageAnnualReturnInceptionDate	Apr. 29, 2005
Parnassus Mid Cap Fund | Russell Midcap Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
One Year	rr_AverageAnnualReturnYear01	13.22%
Five Years	rr_AverageAnnualReturnYear05	17.19%
Since Inception	rr_AverageAnnualReturnSinceInception	10.29%
Parnassus Mid Cap Fund | Lipper Mid-Cap Core Average
Risk/Return:	rr_RiskReturnAbstract
One Year	rr_AverageAnnualReturnYear01	8.24%
Five Years	rr_AverageAnnualReturnYear05	14.61%
Since Inception	rr_AverageAnnualReturnSinceInception	8.94%

[1] The investment adviser has contractually agreed to reduce its investment advisory fee to the extent necessary to limit total operating expenses to 0.99% of net assets for the Parnassus Mid Cap Fund—Investor Shares and to 0.85% of net assets for the Parnassus Mid Cap Fund—Institutional Shares. This agreement will not be terminated prior to May 1, 2017, and may be continued indefinitely by the investment adviser on a year-to-year basis.

[2] Other expenses have been estimated based on actual expenses of the Investor Shares during the fiscal year ended December 31, 2014.