Performance Management - American Century Mutual Funds, Inc |
Mar. 01, 2026 |
|---|---|
| BALANCED FUND | |
| Prospectus [Line Items] | |
| Bar Chart and Performance Table [Heading] | Fund Performance |
| Performance Narrative [Text Block] | The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. The table also shows returns for a blended index, which the advisor considers to be more representative of the fund’s investment strategy. The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. For current performance information, please visit americancentury.com. The blended index combines two widely known indices in proportion to the asset mix of the fund. Accordingly, 60% of the index is represented by the S&P 500 Index, which reflects the approximately 60% of the fund’s assets invested in stocks. The blended index’s remaining 40% is represented by the Bloomberg U.S. Aggregate Bond Index, which reflects the roughly 40% of the fund’s assets invested in fixed-income securities. Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
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| Performance Past Does Not Indicate Future [Text] | The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. |
| Performance Information Illustrates Variability of Returns [Text] | The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. |
| Performance Additional Market Index [Text] | The table also shows returns for a blended index, which the advisor considers to be more representative of the fund’s investment strategy. |
| Bar Chart Does Not Reflect Sales Loads [Text] | Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown. |
| Bar Chart [Heading] | Calendar Year Total Returns |
| Bar Chart Closing [Text Block] | Highest Performance Quarter (2Q 2020): 13.21% Lowest Performance Quarter (2Q 2022): -12.34% |
| Performance Table Heading | Average Annual Total ReturnsFor the calendar year ended December 31, 2025 |
| Performance Table Uses Highest Federal Rate | 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 | 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 IRAs. |
| Performance Table One Class of after Tax Shown [Text] | The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary. |
| Index No Deduction for Fees, Expenses, or Taxes [Text] | (reflects no deduction for fees, expenses or taxes) |
| Performance Table Closing [Text Block] | The after-tax returns are shown only for Investor Class shares. After-tax returns for 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 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 IRAs.
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| Performance Availability Website Address [Text] | americancentury.com |
| BALANCED FUND | BALANCED FUND, INVESTOR CLASS | |
| Prospectus [Line Items] | |
| Highest Quarterly Return, Label [Optional Text] | Highest Performance Quarter |
| Highest Quarterly Return | 13.21% |
| Highest Quarterly Return, Date | Jun. 30, 2020 |
| Lowest Quarterly Return, Label [Optional Text] | Lowest Performance Quarter |
| Lowest Quarterly Return | (12.34%) |
| Lowest Quarterly Return, Date | Jun. 30, 2022 |
| GROWTH FUND | |
| Prospectus [Line Items] | |
| Bar Chart and Performance Table [Heading] | Fund Performance |
| Performance Narrative [Text Block] | The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. The table also shows returns for the Russell 1000® Growth Index, which the advisor considers to be more representative of the fund’s investment strategy. The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. For current performance information, please visit americancentury.com. Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
|
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. |
| Performance Information Illustrates Variability of Returns [Text] | The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. |
| Performance Additional Market Index [Text] | The table also shows returns for the Russell 1000® Growth Index, which the advisor considers to be more representative of the fund’s investment strategy. |
| Bar Chart Does Not Reflect Sales Loads [Text] | Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown. |
| Bar Chart [Heading] | Calendar Year Total Returns |
| Bar Chart Closing [Text Block] | Highest Performance Quarter (2Q 2020): 27.93% Lowest Performance Quarter (2Q 2022): -22.01%
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| Performance Table Heading | Average Annual Total ReturnsFor the calendar year ended December 31, 2025 |
| Performance Table Uses Highest Federal Rate | 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 | 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 IRAs. |
| Performance Table One Class of after Tax Shown [Text] | The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary. |
| Index No Deduction for Fees, Expenses, or Taxes [Text] | (reflects no deduction for fees, expenses or taxes) |
| Performance Table Closing [Text Block] | The after-tax returns are shown only for Investor Class shares. After-tax returns for 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 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 IRAs.
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| Performance Availability Website Address [Text] | americancentury.com. |
| GROWTH FUND | GROWTH FUND, INVESTOR CLASS | |
| Prospectus [Line Items] | |
| Highest Quarterly Return, Label [Optional Text] | Highest Performance Quarter |
| Highest Quarterly Return | 27.93% |
| Highest Quarterly Return, Date | Jun. 30, 2020 |
| Lowest Quarterly Return, Label [Optional Text] | Lowest Performance Quarter |
| Lowest Quarterly Return | (22.01%) |
| Lowest Quarterly Return, Date | Jun. 30, 2022 |
| HERITAGE FUND | |
| Prospectus [Line Items] | |
| Bar Chart and Performance Table [Heading] | Fund Performance |
| Performance Narrative [Text Block] | The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. The table also shows returns for the Russell Midcap® Growth Index, which the advisor considers to be more representative of the fund’s investment strategy. The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. For current performance information, please visit americancentury.com. Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
|
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. |
| Performance Information Illustrates Variability of Returns [Text] | The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. |
| Performance Additional Market Index [Text] | The table also shows returns for the Russell Midcap® Growth Index, which the advisor considers to be more representative of the fund’s investment strategy. |
| Bar Chart Does Not Reflect Sales Loads [Text] | Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown. |
| Bar Chart [Heading] | Calendar Year Total Returns |
| Bar Chart Closing [Text Block] | Highest Performance Quarter (2Q 2020): 32.32% Lowest Performance Quarter (2Q 2022): -22.31% |
| Performance Table Heading | Average Annual Total ReturnsFor the calendar year ended December 31, 2025 |
| Performance Table Uses Highest Federal Rate | 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 | 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 IRAs. |
| Performance Table One Class of after Tax Shown [Text] | The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary. |
| Index No Deduction for Fees, Expenses, or Taxes [Text] | (reflects no deduction for fees, expenses or taxes) |
| Performance Table Closing [Text Block] | The after-tax returns are shown only for Investor Class shares. After-tax returns for 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 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 IRAs.
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| Performance Availability Website Address [Text] | americancentury.com |
| HERITAGE FUND | HERITAGE FUND, INVESTOR CLASS | |
| Prospectus [Line Items] | |
| Highest Quarterly Return, Label [Optional Text] | Highest Performance Quarter |
| Highest Quarterly Return | 32.32% |
| Highest Quarterly Return, Date | Jun. 30, 2020 |
| Lowest Quarterly Return, Label [Optional Text] | Lowest Performance Quarter |
| Lowest Quarterly Return | (22.31%) |
| Lowest Quarterly Return, Date | Jun. 30, 2022 |
| LARGE CAP EQUITY FUND | |
| Prospectus [Line Items] | |
| Bar Chart and Performance Table [Heading] | Fund Performance |
| Performance Narrative [Text Block] | The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with 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. For current performance information, please visit americancentury.com. Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
|
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. |
| Performance Information Illustrates Variability of Returns [Text] | The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. |
| Bar Chart Does Not Reflect Sales Loads [Text] | Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown. |
| Bar Chart [Heading] | Calendar Year Total Returns |
| Bar Chart Closing [Text Block] | Highest Performance Quarter (2Q 2020): 21.24% Lowest Performance Quarter (1Q 2020): -18.99% |
| Performance Table Heading | Average Annual Total Returns For the calendar year ended December 31, 2025 |
| Performance Table Uses Highest Federal Rate | 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 | 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 IRAs. |
| Performance Table One Class of after Tax Shown [Text] | The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary. |
| Index No Deduction for Fees, Expenses, or Taxes [Text] | (reflects no deduction for fees, expenses or taxes) |
| Performance Table Closing [Text Block] | The after-tax returns are shown only for Investor Class shares. After-tax returns for 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 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 IRAs. |
| Performance Availability Website Address [Text] | americancentury.com |
| LARGE CAP EQUITY FUND | LARGE CAP EQUITY FUND, INVESTOR CLASS | |
| Prospectus [Line Items] | |
| Highest Quarterly Return, Label [Optional Text] | Highest Performance Quarter |
| Highest Quarterly Return | 21.24% |
| Highest Quarterly Return, Date | Jun. 30, 2020 |
| Lowest Quarterly Return, Label [Optional Text] | Lowest Performance Quarter |
| Lowest Quarterly Return | (18.99%) |
| Lowest Quarterly Return, Date | Mar. 31, 2020 |
| SELECT FUND | |
| Prospectus [Line Items] | |
| Bar Chart and Performance Table [Heading] | Fund Performance |
| Performance Narrative [Text Block] | The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. The table also shows returns for the Russell 1000® Growth Index, which the advisor considers to be more representative of the fund’s investment strategy. The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. For current performance information, please visit americancentury.com. Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
|
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. |
| Performance Information Illustrates Variability of Returns [Text] | The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. |
| Performance Additional Market Index [Text] | The table also shows returns for the Russell 1000® Growth Index, which the advisor considers to be more representative of the fund’s investment strategy. |
| Bar Chart Does Not Reflect Sales Loads [Text] | Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown. |
| Bar Chart [Heading] | Calendar Year Total Returns |
| Bar Chart Closing [Text Block] | Highest Performance Quarter (2Q 2020): 26.28% Lowest Performance Quarter (2Q 2022): -20.81%
|
| Performance Table Heading | Average Annual Total ReturnsFor the calendar year ended December 31, 2025 |
| Performance Table Uses Highest Federal Rate | 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 | 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 IRAs. |
| Performance Table One Class of after Tax Shown [Text] | The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary. |
| Index No Deduction for Fees, Expenses, or Taxes [Text] | (reflects no deduction for fees, expenses or taxes) |
| Performance Table Closing [Text Block] | The after-tax returns are shown only for Investor Class shares. After-tax returns for 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 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 IRAs.
|
| Performance Availability Website Address [Text] | americancentury.com |
| SELECT FUND | SELECT FUND, INVESTOR CLASS | |
| Prospectus [Line Items] | |
| Highest Quarterly Return, Label [Optional Text] | Highest Performance Quarter |
| Highest Quarterly Return | 26.28% |
| Highest Quarterly Return, Date | Jun. 30, 2020 |
| Lowest Quarterly Return, Label [Optional Text] | Lowest Performance Quarter |
| Lowest Quarterly Return | (20.81%) |
| Lowest Quarterly Return, Date | Jun. 30, 2022 |
| SMALL CAP GROWTH FUND | |
| Prospectus [Line Items] | |
| Bar Chart and Performance Table [Heading] | Fund Performance |
| Performance Narrative [Text Block] | The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. The table also shows returns for the Russell 2000® Growth Index, which the advisor considers to be more representative of the fund’s investment strategy. The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. For current performance information, please visit americancentury.com. Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
|
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. |
| Performance Information Illustrates Variability of Returns [Text] | The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. |
| Performance Additional Market Index [Text] | The table also shows returns for the Russell 2000® Growth Index, which the advisor considers to be more representative of the fund’s investment strategy. |
| Bar Chart Does Not Reflect Sales Loads [Text] | Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown. |
| Bar Chart [Heading] | Calendar Year Total Returns |
| Bar Chart Closing [Text Block] | Highest Performance Quarter (2Q 2020): 34.92% Lowest Performance Quarter (4Q 2018): -21.25% |
| Performance Table Heading | Average Annual Total ReturnsFor the calendar year ended December 31, 2025 |
| Performance Table Uses Highest Federal Rate | 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 | 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 IRAs. |
| Performance Table One Class of after Tax Shown [Text] | The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary. |
| Index No Deduction for Fees, Expenses, or Taxes [Text] | (reflects no deduction for fees, expenses or taxes) |
| Performance Table Closing [Text Block] | The after-tax returns are shown only for Investor Class shares. After-tax returns for 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 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 IRAs. |
| Performance Availability Website Address [Text] | americancentury.com |
| SMALL CAP GROWTH FUND | SMALL CAP GROWTH FUND, INVESTOR CLASS | |
| Prospectus [Line Items] | |
| Highest Quarterly Return, Label [Optional Text] | Highest Performance Quarter |
| Highest Quarterly Return | 34.92% |
| Highest Quarterly Return, Date | Jun. 30, 2020 |
| Lowest Quarterly Return, Label [Optional Text] | Lowest Performance Quarter |
| Lowest Quarterly Return | (21.25%) |
| Lowest Quarterly Return, Date | Dec. 31, 2018 |
| ULTRA FUND | |
| Prospectus [Line Items] | |
| Bar Chart and Performance Table [Heading] | Fund Performance |
| Performance Narrative [Text Block] | The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. The table also shows returns for the Russell 1000® Growth Index, which the advisor considers to be more representative of the fund’s investment strategy. The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. For current performance information, please visit americancentury.com. Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
|
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. |
| Performance Information Illustrates Variability of Returns [Text] | The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. |
| Performance Additional Market Index [Text] | The table also shows returns for the Russell 1000® Growth Index, which the advisor considers to be more representative of the fund’s investment strategy. |
| Bar Chart Does Not Reflect Sales Loads [Text] | Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown. |
| Bar Chart [Heading] | Calendar Year Total Returns |
| Bar Chart Closing [Text Block] | Highest Performance Quarter (2Q 2020): 32.22% Lowest Performance Quarter (2Q 2022): -23.70% |
| Performance Table Heading | Average Annual Total ReturnsFor the calendar year ended December 31, 2025 |
| Performance Table Uses Highest Federal Rate | 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 | 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 IRAs. |
| Performance Table One Class of after Tax Shown [Text] | The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary. |
| Index No Deduction for Fees, Expenses, or Taxes [Text] | (reflects no deduction for fees, expenses or taxes) |
| Performance Table Closing [Text Block] | The after-tax returns are shown only for Investor Class shares. After-tax returns for 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 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 IRAs.
|
| Performance Availability Website Address [Text] | americancentury.com |
| ULTRA FUND | ULTRA FUND, INVESTOR CLASS | |
| Prospectus [Line Items] | |
| Highest Quarterly Return, Label [Optional Text] | Highest Performance Quarter |
| Highest Quarterly Return | 32.22% |
| Highest Quarterly Return, Date | Jun. 30, 2020 |
| Lowest Quarterly Return, Label [Optional Text] | Lowest Performance Quarter |
| Lowest Quarterly Return | (23.70%) |
| Lowest Quarterly Return, Date | Jun. 30, 2022 |