S000004308 [Member] Investment Strategy - iShares S&P Mid-Cap 400 Growth ETF	Mar. 31, 2026
Prospectus [Line Items]
Strategy [Heading]	Principal Investment Strategies
Strategy Narrative [Text Block]	The Fund seeks to track the investment results of the S&P MidCap 400 Growth IndexTM (the “Underlying Index”), which measures the performance of the mid-capitalization growth sector of the U.S. equity market. It is a subset of the S&P MidCap 400® (the “Parent Index”) and consists of those stocks in the Parent Index exhibiting the strongest growth characteristics, as determined by S&P Dow Jones Indices LLC (the “Index Provider” or “SPDJI”), a subsidiary of S&P Global, Inc. The growth characteristics used by the Index Provider include three-year change in earnings per share over price per share, three-year sales-per-share growth rate and momentum (12-month percentage share price change). To the extent that earnings, sales and price data is not available for the above-listed time periods, the Index Provider will use shorter time periods in accordance with the Index Provider’s methodology. The Underlying Index represented approximately 51.01% of the market capitalization of the Parent Index as of March 31, 2026. As of March 31, 2026, stocks must have a market capitalization between $1.6 billion and $27.9 billion for initial inclusion in the Parent Index; this range and constituents' market capitalization may fluctuate depending on the overall level of the equity markets. The Underlying Index uses a capping methodology at each quarterly rebalance, that limits the weight of any single company to a maximum of 23% of the Underlying Index weight, and the sum of all companies with a weight above 4.8% to an aggregate of 50% of the Underlying Index weight. Additionally, if, on the third to last business day of March, June, September, or December a company has an index weight greater than 24% or the sum of the companies with weights greater than 4.8% exceeds 50%, a secondary reweighting is triggered with the rebalancing effective date after the close of the last business day of the month. As of March 31, 2026, a significant portion of the Underlying Index was represented by securities of companies in the industrials and technology industries or sectors. 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. 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 a product of SPDJI, 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 S&P MidCap 400 Growth IndexTM (the “Underlying Index”), which measures the performance of the mid-capitalization growth sector of the U.S. equity market. It is a subset of the S&P MidCap 400® (the “Parent Index”) and consists of those stocks in the Parent Index exhibiting the strongest growth characteristics, as determined by S&P Dow Jones Indices LLC (the “Index Provider” or “SPDJI”), a subsidiary of S&P Global, Inc. The growth characteristics used by the Index Provider include three-year change in earnings per share over price per share, three-year sales-per-share growth rate and momentum (12-month percentage share price change). To the extent that earnings, sales and price data is not available for the above-listed time periods, the Index Provider will use shorter time periods in accordance with the Index Provider’s methodology. The Underlying Index represented approximately 51.01% of the market capitalization of the Parent Index as of March 31, 2026. As of March 31, 2026, stocks must have a market capitalization between $1.6 billion and $27.9 billion for initial inclusion in the Parent Index; this range and constituents' market capitalization may fluctuate depending on the overall level of the equity markets.

The Underlying Index uses a capping methodology at each quarterly rebalance, that limits the weight of any single company to a maximum of 23% of the Underlying Index weight, and the sum of all companies with a weight above 4.8% to an aggregate of 50% of the Underlying Index weight. Additionally, if, on the third to last business day of March, June, September, or December a company has an index weight greater than 24% or the sum of the companies with weights greater than 4.8% exceeds 50%, a secondary reweighting is triggered with the rebalancing effective date after the close of the last business day of the month.

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.