Investor A Institutional [Member] Performance Management - Investor A Institutional [Member] - iShares Total U.S. Stock Market Index Fund	Jul. 31, 2025
Prospectus [Line Items]
Bar Chart and Performance Table [Heading]	Performance Information
Performance Narrative [Text Block]	The information shows you how the performance of the Fund has varied for the periods since inception and provides some indication of the risks of investing in the Fund. The table compares the Fund’s performance to that of the Russell 3000^® Index. 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 BlackRock 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.
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 performance of the Fund has varied for the periods since inception and provides some indication of the risks of investing in the Fund.
Bar Chart [Heading]	Investor A Shares ANNUAL TOTAL RETURNS iShares Total U.S. Stock Market Index Fund As of 12/31
Bar Chart Closing [Text Block]	During the periods shown in the bar chart, the highest return for a quarter was 21.80% (quarter ended June 30, 2020) and the lowest return for a quarter was -20.94% (quarter ended March 31, 2020). The year-to-date return as of September 30, 2025 was 14.11%.
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. After-tax returns are shown for Investor A Shares only, and the after-tax returns for Institutional Shares will vary.
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 Table One Class of after Tax Shown [Text]	After-tax returns are shown for Investor A Shares only, and the after-tax returns for Institutional Shares will vary.
Performance Availability Website Address [Text]	www.blackrock.com
Performance Availability Phone [Text]	(800) 882-0052
Investor A
Prospectus [Line Items]
Year to Date Return, Label [Optional Text]	year-to-date return
Bar Chart, Year to Date Return	14.11%
Bar Chart, Year to Date Return, Date	Sep. 30, 2025
Highest Quarterly Return, Label [Optional Text]	highest return
Highest Quarterly Return	21.80%
Highest Quarterly Return, Date	Jun. 30, 2020
Lowest Quarterly Return, Label [Optional Text]	lowest return
Lowest Quarterly Return	(20.94%)
Lowest Quarterly Return, Date	Mar. 31, 2020

Investor A Institutional [Member] Performance Management - Investor A Institutional [Member] - iShares Total U.S. Stock Market Index Fund

Jul. 31, 2025

Bar Chart and Performance Table [Heading]

Performance Information

Performance Narrative [Text Block]

The information shows you how the performance of the Fund has varied for the periods since inception and provides some indication of the risks of investing in the Fund. The table compares the Fund’s performance to that of the Russell 3000^® Index. 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 BlackRock 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.

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 performance of the Fund has varied for the periods since inception and provides some indication of the risks of investing in the Fund.

Bar Chart [Heading]

Investor A Shares ANNUAL TOTAL RETURNS iShares Total U.S. Stock Market Index Fund As of 12/31

Bar Chart Closing [Text Block]

During the periods shown in the bar chart, the highest return for a quarter was 21.80% (quarter ended June 30, 2020) and the lowest return for a quarter was -20.94% (quarter ended March 31, 2020). The year-to-date return as of September 30, 2025 was 14.11%.

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. After-tax returns are shown for Investor A Shares only, and the after-tax returns for Institutional Shares will vary.

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 Table One Class of after Tax Shown [Text]

After-tax returns are shown for Investor A Shares only, and the after-tax returns for Institutional Shares will vary.

Performance Availability Website Address [Text]

www.blackrock.com

Performance Availability Phone [Text]

(800) 882-0052

Investor A

Prospectus [Line Items]

Year to Date Return, Label [Optional Text]

year-to-date return

Bar Chart, Year to Date Return

14.11%