S000000852 [Member] Performance Management - Parnassus Mid Cap Growth Fund |
Dec. 31, 2025 |
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| Prospectus [Line Items] | |
| Bar Chart and Performance Table [Heading] | Performance Information |
| Performance Narrative [Text Block] | The bar chart and table that follow contain information that allows you to evaluate the Parnassus Mid Cap Growth 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 the 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.
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| Performance Past Does Not Indicate Future [Text] | How the Fund performed in the past (before and after taxes) is not necessarily an indication of how it will perform in the future. |
| Performance Information Illustrates Variability of Returns [Text] | The bar chart and table that follow contain information that allows you to evaluate the Parnassus Mid Cap Growth 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. |
| Bar Chart [Heading] | Annual Total Returns (%) |
| Bar Chart Closing [Text Block] | During the ten‑year period shown in the bar chart, the highest return for a quarter was 25.78% (quarter ended June 30, 2020), and the lowest return for a quarter was a loss of 21.94% (quarter ended June 30, 2022).
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| Performance Table Heading | Average Annual Total Returns (%)(all periods ended December 31, 2025) |
| Performance Table Narrative | Following is a table comparing the performance of the Parnassus Mid Cap Growth Fund’s two share classes with that of the Russell Midcap® Growth Index and Russell 1000® Index. Figures are average annual returns for the one‑, five- and ten‑year periods ended December 31, 2025. The table is intended to demonstrate the risk of investing in the Parnassus Mid Cap Growth 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® Growth Index and Russell 1000® Index, and also how the Fund’s performance varies from year to year.
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| Performance Table Uses Highest Federal Rate | The after‑tax returns are calculated using the historical highest individual stated federal marginal income tax rates and do not reflect the impact of state and local taxes. |
| Performance Table Not Relevant to Tax Deferred | After‑tax returns are not relevant to investors who hold their Fund shares through tax‑advantaged arrangements, such as 401(k) plans or individual retirement accounts. |
| Performance Table Explanation after Tax Higher | Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a tax benefit of realizing a capital loss upon the sale of Fund shares. |
| Performance Table One Class of after Tax Shown [Text] | After‑tax returns are shown for Investor Shares only. After‑tax returns for Institutional Shares will vary. |
| Performance Table Closing [Text Block] | The after‑tax returns are calculated using the historical highest individual stated 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 individual tax situation and may differ from those shown. After‑tax returns are not relevant to investors who hold their Fund shares through tax‑advantaged arrangements, such as 401(k) plans or individual retirement accounts. Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a tax benefit of realizing a capital loss upon the sale of Fund shares. After‑tax returns are shown for Investor Shares only. After‑tax returns for Institutional Shares will vary.
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| Performance Availability Website Address [Text] | www.parnassus.com |
| Performance Availability Phone [Text] | (800) 999‑3505 |
| Investor Shares | |
| Prospectus [Line Items] | |
| Highest Quarterly Return, Label [Optional Text] | highest return |
| Highest Quarterly Return | 25.78% |
| Highest Quarterly Return, Date | Jun. 30, 2020 |
| Lowest Quarterly Return, Label [Optional Text] | lowest return |
| Lowest Quarterly Return | (21.94%) |
| Lowest Quarterly Return, Date | Jun. 30, 2022 |