Class K [Member] Performance Management - Class K - BLACKROCK LARGE CAP FOCUS GROWTH FUND, INC. |
May 31, 2025 |
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| Prospectus [Line Items] | |
| Bar Chart and Performance Table [Heading] | Performance Information |
| Performance Narrative [Text Block] | The information shows you how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. Class K Shares commenced operations on November 25, 2019. As a result, the returns shown below for Class K Shares prior to November 25, 2019 are those of the Fund’s Institutional Shares, which are not offered in this prospectus. The performance of Class K Shares would be substantially similar to Institutional Shares because Class K Shares and Institutional Shares are invested in the same portfolio of securities and performance would differ only to the extent that Class K Shares and Institutional Shares have different expenses. The actual returns of Class K Shares would have been higher than those of Institutional Shares because Class K Shares have lower expenses than Institutional Shares. The table compares the Fund’s performance to that of the Russell 1000® Index and the Russell 1000® Growth Index. The Russell 1000® Growth Index is relevant to the Fund because it has characteristics similar to the Fund’s investment strategy. To the extent that dividends and distributions have been paid by the Fund, the performance information for the Fund in the chart and table assumes reinvestment of the dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. The table includes all applicable fees. If the Fund’s investment manager and its affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund’s returns would have been lower. Updated information on the Fund’s performance, including its current net asset value, can be obtained by visiting www.blackrock.com or can be obtained by phone at 800-882-0052.
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| Performance Past Does Not Indicate Future [Text] | As with all such investments, past performance (before and after taxes) is not an indication of future results. |
| Performance Information Illustrates Variability of Returns [Text] | The information shows you how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. |
| Performance Additional Market Index [Text] | The table compares the Fund’s performance to that of the Russell 1000® Index and the Russell 1000® Growth Index. The Russell 1000® Growth Index is relevant to the Fund because it has characteristics similar to the Fund’s investment strategy. |
| Bar Chart [Heading] | Class K Shares ANNUAL TOTAL RETURNS BlackRock Large Cap Focus Growth Fund, Inc. As of 12/31 |
| Bar Chart Closing [Text Block] | During the ten-year period shown in the bar chart, the highest return for a quarter was 29.71% (quarter ended June 30, 2020) and the lowest return for a quarter was -22.90% (quarter ended June 30, 2022). The year-to-date return as of June 30, 2025 was 7.31%.
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| Performance Table Heading | For the periods ended 12/31/24Average Annual Total Returns |
| Performance Table Narrative | 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 tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
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| 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 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 tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. |
| Performance Availability Website Address [Text] | www.blackrock.com |
| Performance Availability Phone [Text] | 800-882-0052 |
| Class K Shares | |
| Prospectus [Line Items] | |
| Year to Date Return, Label [Optional Text] | year-to-date return |
| Bar Chart, Year to Date Return | 7.31% |
| Bar Chart, Year to Date Return, Date | Jun. 30, 2025 |
| Highest Quarterly Return, Label [Optional Text] | highest return |
| Highest Quarterly Return | 29.71% |
| Highest Quarterly Return, Date | Jun. 30, 2020 |
| Lowest Quarterly Return, Label [Optional Text] | lowest return |
| Lowest Quarterly Return | (22.90%) |
| Lowest Quarterly Return, Date | Jun. 30, 2022 |