S000004436 [Member] Investment Strategy - iShares ESG Optimized MSCI USA ETF	Apr. 30, 2026
Prospectus [Line Items]
Strategy [Heading]	Principal Investment Strategies
Strategy Narrative [Text Block]	The Fund seeks to track the investment results of the MSCI USA Extended ESG Select Index (the “Underlying Index”), which is an optimized index designed to maximize exposure to positive environmental, social and governance (“ESG”) characteristics, while exhibiting risk and return characteristics similar to the MSCI USA Index. The MSCI USA Index is designed to measure the performance of the large- and mid-capitalization segments of the U.S. equities market. As of April 30, 2026, the Underlying Index consisted of 170 securities selected from the MSCI USA Index. MSCI Inc. (the “Index Provider” or “MSCI”) analyzes each eligible company’s ESG performance using proprietary ratings covering ESG and ethics criteria. The index methodology is designed so that companies with relatively high overall ratings have a higher representation in the Underlying Index than in the MSCI USA Index and companies with relatively low overall ratings have a lower representation in the Underlying Index than in the MSCI USA Index. Exceptions may result from the Underlying Index’s objective of having risk and return characteristics similar to the MSCI USA Index. At each quarterly review, the Underlying Index must have an ESG score of at least 20% better than that of the MSCI USA Index, as determined by the Index Provider. The Index Provider excludes securities of companies involved in the business of tobacco, alcohol, gambling, nuclear power and weapons, fossil fuel extraction, thermal coal power and unconventional oil and gas businesses (e.g., thermal coal extraction and generation or oil sands extraction), companies involved with conventional and controversial weapons, producers and major retailers of civilian firearms, as well as companies involved in very severe business controversies. The Index Provider defines a controversy as an instance or ongoing situation in which company operations and/or products allegedly have a negative environmental, social and/or governance impact. Each controversy case is assessed for the severity of its impact on society. The Index Provider generally classifies companies as “involved” in a particular business based on revenue or percentage of revenue thresholds (e.g., 10%) for certain products and activities in an excluded industry. The securities of certain companies are excluded regardless of revenue measures (e.g., all companies involved in the manufacturing of controversial weapons are excluded). To maintain risk and return characteristics similar to the MSCI USA Index, the Index Provider applies various optimization constraints (e.g., constituent and sector weights relative to the parent index). The Index Provider also applies conditional capping to the index constituents. At the quarterly review, if the combined weight of issuers with individual weights above 4.5% exceeds 22.5% of the Underlying Index, then the total weight is capped at 22.5%. The Index Provider also verifies at the end of each business day whether the combined weight of issuers with individual weights above 5% exceeds 25% of the Underlying Index. If this daily threshold is breached, rebalancing occurs to meet the prescribed 4.5% and 22.5% buffer levels. The optimization constraints are not applied during a rebalancing triggered by daily capping. As of April 30, 2026, a significant portion of the Underlying Index was represented by securities of companies in the technology industry or sector. The components of the Underlying Index are likely to change over time. The Fund seeks to track the investment results of the Underlying Index before fees and expenses of the Fund. BFA uses a representative sampling indexing strategy to manage the Fund. “Representative sampling” is an indexing strategy that involves investing in a representative sample of securities or other instruments intended to collectively have an investment profile similar to that of an applicable underlying index. The instruments selected are expected to have, in the aggregate, investment characteristics (based on factors such as market capitalization and industry weightings), fundamental characteristics (such as return variability and yield) and liquidity measures similar to those of an applicable underlying index. The Fund may or may not hold all of the components of the Underlying Index. The Fund may use derivatives to gain or reduce exposure to the components of the Underlying Index or exposure to one or more market risk factors associated with such components. Subject to the limits described herein, the Fund may purchase and hold cash and cash equivalents, including shares of money market funds advised by BFA or its affiliates, and may also purchase and hold instruments not included in the Underlying Index when BFA believes that such instruments will help the Fund track the performance of the Underlying Index over time, including in light of expected liquidity or trading costs, anticipated additions to or deletions from the Underlying Index, or other reasons as determined by BFA. In accordance with Rule 35d-1 under the Investment Company Act of 1940, as amended (the “1940 Act”), under normal circumstances, the Fund will not invest less than 80% of the value of its net assets, plus the amount of any borrowings for investment purposes, in components of its Underlying Index. Investments in derivatives and other investments will be counted toward the Fund's 80% investment policy to the extent that they provide exposure to the components of its Underlying Index or exposure to one or more market risk factors associated with such components. The Fund's 80% investment policy may be changed by the Trust's Board of Trustees (the “Board”) upon 60 days' notice to shareholders. In addition, the Fund generally will invest at least 90% of its assets in the components of the Underlying Index. The Fund may lend securities representing up to one-third of the value of the Fund's total assets (including the value of any collateral received). The Underlying Index is sponsored by MSCI, which is independent of the Fund and BFA. The Index Provider determines the composition and relative weightings of the components of the Underlying Index and publishes information regarding the market value of the Underlying Index. Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. For purposes of this limitation, securities of the U.S. government (including its agencies and instrumentalities) and repurchase agreements collateralized by U.S. government securities are not considered to be issued by members of any industry.
Strategy Portfolio Concentration [Text]	Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. For purposes of this limitation, securities of the U.S. government (including its agencies and instrumentalities) and repurchase agreements collateralized by U.S. government securities are not considered to be issued by members of any industry.

The Fund seeks to track the investment results of the MSCI USA Extended ESG Select Index (the “Underlying Index”), which is an optimized index designed to maximize exposure to positive environmental, social and governance (“ESG”) characteristics, while exhibiting risk and return characteristics similar to the MSCI USA Index. The MSCI USA Index is designed to measure the performance of the large- and mid-capitalization segments of the U.S. equities market. As of April 30, 2026, the Underlying Index consisted of 170 securities selected from the MSCI USA Index.

MSCI Inc. (the “Index Provider” or “MSCI”) analyzes each eligible company’s ESG performance using proprietary ratings covering ESG and ethics criteria. The index methodology is designed so that companies with relatively high overall ratings have a higher representation in the Underlying Index than in the MSCI USA Index and companies with relatively low overall ratings have a lower representation in the Underlying Index than in the MSCI USA Index. Exceptions may result from the Underlying Index’s objective of having risk and return characteristics similar to the MSCI USA Index. At each quarterly review, the Underlying Index must have an ESG score of at least 20% better than that of the MSCI USA Index, as determined by the Index Provider.

The Index Provider excludes securities of companies involved in the business of tobacco, alcohol, gambling, nuclear power and weapons, fossil fuel extraction, thermal coal power and unconventional oil and gas businesses (e.g., thermal coal extraction and generation or oil sands extraction), companies involved with conventional and controversial weapons, producers and major retailers of civilian firearms, as well as companies involved in very severe business controversies. The

Index Provider defines a controversy as an instance or ongoing situation in which company operations and/or products allegedly have a negative environmental, social and/or governance impact. Each controversy case is assessed for the severity of its impact on society. The Index Provider generally classifies companies as “involved” in a particular business based on revenue or percentage of revenue thresholds (e.g., 10%) for certain products and activities in an excluded industry. The securities of certain companies are excluded regardless of revenue measures (e.g., all companies involved in the manufacturing of controversial weapons are excluded).

To maintain risk and return characteristics similar to the MSCI USA Index, the Index Provider applies various optimization constraints (e.g., constituent and sector weights relative to the parent index). The Index Provider also applies conditional capping to the index constituents. At the quarterly review, if the combined weight of issuers with individual weights above 4.5% exceeds 22.5% of the Underlying Index, then the total weight is capped at 22.5%. The Index Provider also verifies at the end of each business day whether the combined weight of issuers with individual weights above 5% exceeds 25% of the Underlying Index. If this daily threshold is breached, rebalancing occurs to meet the prescribed 4.5% and 22.5% buffer levels. The optimization constraints are not applied during a rebalancing triggered by daily capping.

The Fund seeks to track the investment results of the Underlying Index before fees and expenses of the Fund. BFA uses a representative sampling indexing strategy to manage the Fund. “Representative sampling” is an indexing strategy that involves investing in a representative sample of securities or other instruments intended to collectively have an investment profile similar to that of an applicable underlying index. The instruments selected are expected to have, in the aggregate, investment characteristics (based on factors such as market capitalization and industry weightings), fundamental characteristics (such as return variability and yield) and liquidity measures similar to those of an applicable underlying index. The Fund may or may not hold all of the components of the Underlying Index. The Fund may use derivatives to gain or reduce exposure to the components of the Underlying Index or exposure to one or more market risk factors associated with such components. Subject to the limits described herein, the Fund may purchase and hold cash and cash equivalents, including shares of money market funds advised by BFA or its affiliates, and may also purchase and hold instruments not included in the Underlying Index when BFA believes that such instruments will help the Fund track the performance of the Underlying Index over time, including in light of expected liquidity or trading costs, anticipated additions to or deletions from the Underlying Index, or other reasons as determined by BFA.

In accordance with Rule 35d-1 under the Investment Company Act of 1940, as amended (the “1940 Act”), under normal circumstances, the Fund will not invest less than 80% of the value of its net assets, plus the amount of any borrowings for investment purposes, in components of its Underlying Index. Investments in derivatives and other investments will be counted toward the Fund's 80% investment policy to the extent that they provide exposure to the components of its Underlying Index or exposure to one or more market risk factors associated with such components. The Fund's 80% investment policy may be changed by the Trust's Board of Trustees (the “Board”) upon 60 days' notice to shareholders.

Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. For purposes of this limitation, securities of the U.S. government (including its agencies and instrumentalities) and repurchase agreements collateralized by U.S. government securities are not considered to be issued by members of any industry.