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BlackRock U.S. Carbon Transition Readiness ETF  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading BLACKROCK U.S. CARBON TRANSITION READINESS ETF Ticker: LCTU      Stock Exchange: NYSE Arca
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The BlackRock U.S. Carbon Transition Readiness ETF (the “Fund”) seeks long-term capital appreciation by investing in large- and mid-capitalization U.S. equity securities that may be better positioned to benefit from the transition to a low-carbon economy.
Expense [Heading] rr_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
The following table describes the fees and expenses that you will incur if you buy, hold and sell shares of the Fund. The investment advisory agreement between BlackRock ETF Trust (the “Trust”) and BlackRock Fund Advisors (“BFA”) provides that BFA will pay all operating expenses of the Fund, except: (i) the management fees, (ii) interest expenses, (iii) taxes, (iv) expenses incurred with respect to the acquisition and disposition of portfolio securities and the execution of portfolio transactions, including brokerage commissions, (v) distribution fees or expenses, and (vi) litigation expenses and any extraordinary expenses. The Fund may incur “Acquired Fund Fees and Expenses.” Acquired Fund Fees and Expenses reflect the Fund’s pro rata share of the fees and expenses incurred indirectly by the Fund as a result of investing in other investment companies. The impact of Acquired Fund Fees and Expenses is included in the total returns of the Fund.
You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the table and Example below.
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses(ongoing expenses that you pay each year as apercentage of the value of your investments)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination June 30, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
The Fund may pay transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a
taxable account. These costs, which are not reflected in the Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. For the fiscal year ended July 31, 2024, the Fund’s portfolio turnover rate was 46% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 46.00%
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock This Example is intended to help you compare the cost of owning shares of the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same.Although your actual costs may be higher or lower, based on these assumptions, your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Fund seeks to outperform the price and yield performance of the Russell 1000® Index (the “Underlying Index”) before including Fund expenses by optimizing for Low Carbon Economy Transition Readiness (“LCETR”) scores criteria based on proprietary BFA research. Under normal circumstances, the Fund seeks to invest at least 80% of its net assets plus the amount of any borrowings for investment purposes in equity securities of issuers listed in the United States of America.
The Fund selects portfolio securities that are components of the Underlying Index. The Underlying Index measures the performance of the large- and mid-capitalization sectors of the U.S. equity market, as defined by FTSE Russell (“Russell”). The components of the Underlying Index are likely to change over time. The Fund may or may not hold all of the securities in the Underlying Index.
The Fund utilizes BFA’s proprietary LCETR strategy to overweight, relative to the Underlying Index, issuers that BFA believes are best positioned to benefit from the transition to a low-carbon economy, and to underweight issuers that it believes are poorly positioned to so benefit. BFA assigns a transition readiness score to each issuer by aggregating research-driven insights across different sustainability themes, which may include, but are not limited to, Energy Production, Clean Technology, Energy Management, Waste Management and Water Management, and weights such scores according to what BFA believes are their relative importance. BFA uses the final score for each issuer to determine whether the Fund should overweight or underweight such issuer based on the issuer’s score in comparison to other issuers in the peer industry. BFA’s methodology seeks to maximize the Fund’s exposure to issuers with the highest LCETR scores while controlling for risk. The Fund may invest in issuers in all industries represented in the Fund’s Underlying Index, including those issuers that could be considered outside of LCETR investing.
The Fund may invest in large- and mid-capitalization companies.
Equity securities in which the Fund may invest include common stocks, preferred stocks, warrants, depositary receipts, ETFs and equity interests in real estate investment trusts (“REITs”) and master limited partnerships (“MLPs”). The Fund may also purchase convertible securities.
The Fund may invest in certain futures, options and swap contracts.
The Underlying Index is sponsored by Russell, which is part of the London Stock Exchange Group and is independent of the Fund and BFA. Russell determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index.
Risk [Heading] rr_RiskHeading Summary of Principal Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
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. The table compares the Fund’s performance to that of the Russell 1000® 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. 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.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns 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 Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-474-2737 (toll free)
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.blackrock.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture As with all such investments, past performance (before and after taxes) is not an indication of future results.
Bar Chart [Heading] rr_BarChartHeading Calendar Year by Year Returns1
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
The best calendar quarter return during the period shown above was 11.53% in the 4th quarter of 2023; the worst was -16.83% in the 2nd quarter of 2022.
Updated performance information, including the Fund’s current NAV, may be obtained by visiting our website at www.blackrock.com or by calling 1-800-474-2737 (toll free).
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (for the periods ended December 31, 2023)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns in the table above are calculated using the historical highest individual U.S. federal marginal income tax rates and do not reflect the impact of state or local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s tax situation and may differ from those shown, and after-tax returns shown are not relevant to tax-exempt investors or investors who hold shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts (“IRAs”).
Performance Table Explanation after Tax Higher rr_PerformanceTableExplanationAfterTaxHigher Fund returns after taxes on distributions and sales of Fund shares are calculated assuming that an investor has sufficient capital gains of the same character from other investments to offset any capital losses from the sale of Fund shares. As a result, Fund returns after taxes on distributions and sales of Fund shares may exceed Fund returns before taxes and/or returns after taxes on distributions.
BlackRock U.S. Carbon Transition Readiness ETF | Risk Lose Money [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock As with any investment, you could lose all or part of your investment in the Fund, and the Fund’s performance could trail that of other investments.
BlackRock U.S. Carbon Transition Readiness ETF | Equity Securities Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Equity Securities Risk. Stock markets are volatile. The price of equity securities fluctuates based on changes in a company’s financial condition and overall market and economic conditions.
BlackRock U.S. Carbon Transition Readiness ETF | Sustainability Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Sustainability Risk. Sustainability risk is an inclusive term to designate investment risk (probability or uncertainty of occurrence of material losses relative to the expected return of an investment) that relates to environmental, social or governance issues.
Sustainability risk around environmental issues includes, but is not limited to, climate risk, both physical and transition risk. Physical risk arises from the physical effects of climate change, acute or chronic. For example, frequent and severe climate-related events can impact products and services and supply chains. Transition risk – whether policy, technology, market or reputation risk – arises from the adjustment to a low‑carbon economy in order to mitigate climate change. Risks related to social issues can include, but are not limited to, labor rights and community relations. Governance-related risks can include but are not limited to risks around board independence, ownership and control, and audit and tax management. These risks can impact an issuer’s operational effectiveness and resilience as well as its
public perception and reputation, affecting its profitability and, in turn, its capital growth and ultimately impacting the value of holdings in the Fund.
These are only examples of sustainability risk factors, and sustainability risk factors do not solely determine the risk profile of the investment. The relevance, severity, materiality and time horizon of sustainability risk factors and other risks can differ significantly across funds.
Sustainability risk can manifest itself through different existing risk types including, but not limited to, market, liquidity, concentration, credit and asset-liability mismatch risk. For example, the Fund may invest in the securities of an issuer that could face potentially reduced revenues or increased expenditures from physical climate risk (e.g., decreased production capacity due to supply chain perturbations, lower sales due to demand shocks or higher operating or capital costs) or transition risk (e.g., decreased demand for carbon-intensive products and services or increased production costs due to changing input prices). As a result, sustainability risk factors may have a material impact on an investment, may increase volatility, may affect liquidity and may have an adverse impact on the value of shares of the Fund.
The impact of those risks may be higher for funds with particular sectoral or geographic concentrations. For example, funds with geographic concentration in locations susceptible to adverse weather conditions where the value of the investments in the funds may be more susceptible to adverse physical climate events, or funds with specific sectoral concentrations, such as investing in industries or issuers with high carbon intensity or high switching costs associated with the transition to low carbon alternatives, may be more impacted by climate transition risks.
All or a combination of these factors may have an unpredictable impact on the Fund’s investments. Under normal market conditions, such events could have a material impact on the value of shares of the Fund.
Assessments of sustainability risk are specific to the asset class and to a fund’s investment objective. Different asset classes require different data and tools to apply heightened scrutiny, assess materiality, and make meaningful differentiation among issuers and assets. To the extent consistent with the Fund’s investment objective, risks are considered and risk managed concurrently, by prioritizing in part based on materiality and on the Fund’s objective.
The impacts of sustainability risk are likely to develop over time, and new sustainability risks may be identified as further data and information regarding sustainability factors and impacts become available.
BlackRock U.S. Carbon Transition Readiness ETF | Low Carbon Exposure Investment Strategy Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Low Carbon Exposure Investment Strategy Risk. The Fund’s strategy of investing in securities of companies with low carbon exposure limits the type and number of investment opportunities available to the Fund and, as a result, the Fund may underperform other funds that do not seek to minimize carbon exposure. The Fund’s low carbon exposure investment strategy may result in the Fund investing in securities or industry sectors that underperform the market.
BlackRock U.S. Carbon Transition Readiness ETF | Risk of Investing in the United States [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Risk of Investing in the United States. Certain changes in the U.S. economy, such as when the U.S. economy weakens or when its financial markets decline, may have an adverse effect on the securities to which the Fund has exposure.
BlackRock U.S. Carbon Transition Readiness ETF | Assets Under Management AUM Risks [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Assets Under Management (AUM) Risk. From time to time, an Authorized Participant (as defined in the Creations and Redemptions section of the Prospectus), a third-party investor, the Fund’s adviser, an affiliate of the Fund’s adviser, or another fund may invest in the Fund and hold its investment for a specific period of time to allow the Fund to achieve size or scale. There can be no assurance that any such entity would not redeem its investment or that the size of the Fund would be maintained at such levels, which could negatively impact the Fund.
BlackRock U.S. Carbon Transition Readiness ETF | Authorized Participant Concentration Risks [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Authorized Participant Concentration Risk. Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund. There are a limited number of institutions that may act as Authorized Participants for the Fund, including on an agency basis on behalf of other market participants. No Authorized Participant is obligated to engage in creation or redemption transactions. To the extent that Authorized Participants exit the business or do not place creation or redemption orders for the Fund and no other Authorized Participant places orders, Fund shares are more likely to trade at a premium or discount to NAV and possibly face trading halts or delisting.
BlackRock U.S. Carbon Transition Readiness ETF | Consumer Discretionary Sector Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Consumer Discretionary Sector Risk. The consumer discretionary sector may be affected by changes in domestic and international economies, exchange and interest rates, supply chains, competition, consumers’ disposable income, consumer preferences, social trends and marketing campaigns.
BlackRock U.S. Carbon Transition Readiness ETF | Consumer Staples Sector Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Consumer Staples Sector Risk. The consumer staples sector may be affected by, among other things, marketing campaigns, changes in consumer demands, government regulations and changes in commodity prices.
BlackRock U.S. Carbon Transition Readiness ETF | Convertible Securities Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Convertible Securities Risk. The market value of a convertible security performs like that of a regular debt security; that is, if market interest rates rise, the value of a convertible security usually falls. In addition, convertible securities are subject to the risk that the issuer will not be able to pay interest, principal or dividends when due, and their market value may change based on changes in the issuer’s credit rating or the market’s perception of the issuer’s creditworthiness. Since it derives a portion of its value from the common stock into which it may be converted, a convertible security is also subject to the same types of market and issuer risks that apply to the underlying common stock, including the potential for increased volatility in the price of the convertible security.
BlackRock U.S. Carbon Transition Readiness ETF | Depositary Receipts Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Depositary Receipts Risk. Depositary receipts are generally subject to the same risks as the foreign securities that they evidence or into which they may be converted. In addition to investment risks associated with the underlying issuer, depositary receipts expose the Fund to additional risks associated with the non‑uniform terms that apply to depositary receipt programs, credit exposure to the depository bank and to the sponsors and other parties with whom the depository bank establishes the programs, currency risk and the risk of an illiquid market for depositary receipts. The issuers of unsponsored depositary receipts are not obligated to disclose information that is, in the United States, considered material. Therefore, there may be less information available regarding these issuers and there may not be a correlation between such information and the market value of the depositary receipts. While depositary receipts provide an alternative to directly purchasing underlying foreign securities in their respective markets and currencies, they continue to be subject to many of the risks associated with investing directly in foreign securities, including political, economic, and currency risk.
BlackRock U.S. Carbon Transition Readiness ETF | Derivatives Risks [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Derivatives Risk. The Fund’s use of derivatives may increase its costs, reduce the Fund’s returns and/or increase volatility. Derivatives involve significant risks, including:
Leverage Risk. The Fund’s use of derivatives can magnify the Fund’s gains and losses. Relatively small market movements may result in large changes in
the value of a derivatives position and can result in losses that greatly exceed the amount originally invested.
Market Risk. Some derivatives are more sensitive to interest rate changes and market price fluctuations than other securities. The Fund could also suffer losses related to its derivatives positions as a result of unanticipated market movements, which losses are potentially unlimited. Finally, BFA may not be able to predict correctly the direction of securities prices, interest rates and other economic factors, which could cause the Fund’s derivatives positions to lose value.
Counterparty Risk. Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will be unable or unwilling to fulfill its contractual obligation, and the related risks of having concentrated exposure to such a counterparty.
Illiquidity Risk. The possible lack of a liquid secondary market for derivatives and the resulting inability of the Fund to sell or otherwise close a derivatives position could expose the Fund to losses and could make derivatives more difficult for the Fund to value accurately.
Operational Risk. The use of derivatives includes the risk of potential operational issues, including documentation issues, settlement issues, systems failures, inadequate controls and human error.
Legal Risk. The risk of insufficient documentation, insufficient capacity or authority of counterparty, or legality or enforceability of a contract.
Volatility and Correlation Risk. Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. A risk of the Fund’s use of derivatives is that the fluctuations in their values may not correlate with the overall securities markets.
Valuation Risk. Valuation for derivatives may not be readily available in the market. Valuation may be more difficult in times of market turmoil since many investors and market makers may be reluctant to purchase complex instruments or quote prices for them.
Hedging Risk. Hedges are sometimes subject to imperfect matching between the derivative and the underlying security, and there can be no assurance that the Fund’s hedging transactions will be effective.
The use of hedging may result in certain adverse tax consequences.
Tax Risk. Certain aspects of the tax treatment of derivative instruments, including swap agreements and commodity-linked derivative instruments, are currently unclear and may be affected by changes in legislation, regulations or other legally binding authority. Such treatment may be less favorable than that given to a direct investment in an underlying asset and may adversely affect the timing, character and amount of income the Fund realizes from its investments.
BlackRock U.S. Carbon Transition Readiness ETF | Energy and Natural Resources Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Energy and Natural Resources Risk. The Fund’s investments in energy and natural resources companies are especially affected by variations in the commodities markets (that may be due to market events, regulatory developments or other factors that the Fund cannot control) and these companies may lack the resources and the broad business lines to weather hard times. Energy companies can be significantly affected by the supply of and demand for specific products and services, the supply of and demand for oil and gas, the price of oil and gas, exploration and production spending, government regulation, world events and economic conditions. Natural resources companies can be significantly affected by events relating to international political developments, energy conservation, the success of exploration projects, commodity prices, and tax and government regulations.
BlackRock U.S. Carbon Transition Readiness ETF | Financial Services Industry Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Financial Services Industry Risk. Because of its concentration in the financial services industry, the Fund will be more susceptible to any economic, business, political or other developments which generally affect this industry sector. As a result, the Fund will be exposed to a large extent to the risks associated with that industry, such as government regulation, the availability and cost of capital funds (including the availability and stability of deposits in the case of deposit-taking institutions), consolidation and general economic conditions. Financial services companies are also exposed to losses if borrowers and other counterparties experience financial problems and/or cannot repay their obligations.
When interest rates go up, the value of securities issued by many types of financial services companies generally goes down. In many countries, financial services and the companies that provide them are regulated by governmental entities, which can increase costs for new services or products and make it difficult to pass increased costs on to consumers. In certain areas, deregulation of financial
services companies has resulted in increased competition and reduced profitability for certain companies.
The profitability of many types of financial services companies may be adversely affected in certain market cycles, including periods of rising interest rates, which may restrict the availability and increase the cost of capital, and declining economic conditions, which may cause credit losses due to financial difficulties of borrowers. Because many types of financial services companies are vulnerable to these economic cycles, the Fund’s investments may lose value during such periods.
BlackRock U.S. Carbon Transition Readiness ETF | Healthcare Related Securities Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Healthcare-Related Securities Risk. Healthcare companies are strongly affected by worldwide scientific or technological developments. Their products may rapidly become obsolete. Many healthcare companies are also subject to significant government regulation and may be affected by changes in governmental policies.
BlackRock U.S. Carbon Transition Readiness ETF | Industrials Sector Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Industrials Sector Risk. Companies in the industrials sector may be adversely affected by changes in the supply of and demand for products and services, product obsolescence, claims for environmental damage or product liability and changes in general economic conditions, among other factors.
BlackRock U.S. Carbon Transition Readiness ETF | Investment in Other Investment Companies Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Investment in Other Investment Companies Risk. As with other investments, investments in other investment companies, including ETFs, are subject to market and selection risk. In addition, if the Fund acquires shares of investment companies, including ones affiliated with the Fund, shareholders bear both their proportionate share of expenses in the Fund (including management and advisory fees) and, indirectly, the expenses of the investment companies (to the extent not offset by BFA through waivers). To the extent the Fund is held by an affiliated fund, the ability of the Fund itself to hold other investment companies may be limited.
BlackRock U.S. Carbon Transition Readiness ETF | Issuer Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Issuer Risk. Fund performance depends on the performance of individual securities to which the Fund has exposure. Changes in the financial condition or credit rating of an issuer of those securities may cause the value of the securities to decline.
BlackRock U.S. Carbon Transition Readiness ETF | Large Shareholder and Large Scale Redemption Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Large Shareholder and Large-Scale Redemption Risk. Certain shareholders, including an Authorized Participant, a third-party investor, the Fund’s adviser or an affiliate of the Fund’s adviser, a market maker,
or another entity, may from time to time own or manage a substantial amount of Fund shares, or may invest in the Fund and hold their investment for a limited period of time. There can be no assurance that any large shareholder or large group of shareholders would not redeem their investment.
Redemptions of a large number of Fund shares could require the Fund to dispose of assets to meet the redemption requests, which can accelerate the realization of taxable income and/or capital gains and cause the Fund to make taxable distributions to its shareholders earlier than the Fund otherwise would have. In addition, under certain circumstances, non-redeeming shareholders may be treated as receiving a disproportionately large taxable distribution during or with respect to such year. In some circumstances, the Fund may hold a relatively large proportion of its assets in cash in anticipation of large redemptions, diluting its investment returns. To the extent the Fund permits redemptions in cash, these large redemptions may also force the Fund to sell portfolio securities when it might not otherwise do so, which may negatively impact the Fund’s NAV, increase the Fund’s brokerage costs and/or have a material effect on the market price of the Fund shares.
BlackRock U.S. Carbon Transition Readiness ETF | Leverage Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Leverage Risk. Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet the applicable requirements of the Investment Company Act of 1940, as amended, and the rules thereunder. Increases and decreases in the value of the Fund’s portfolio will be magnified when the Fund uses leverage.
BlackRock U.S. Carbon Transition Readiness ETF | Market Risk and Selection Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Market Risk and Selection Risk. Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. The value of a security or other asset may decline due to changes in general market conditions, economic trends or events that are not specifically related to the issuer of the security or other asset, or factors that affect a particular issuer or issuers, exchange, country, group of countries, region, market, industry, group of industries, sector or asset class. Local, regional or global events such as war, acts of terrorism, the spread of infectious illness or other public health issues like pandemics or epidemics, recessions, or other events could have a significant impact on the Fund and its investments.
Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.
An outbreak of an infectious coronavirus (COVID‑19) that was first detected in December 2019 developed into a global pandemic that has resulted in numerous disruptions in the market and has had significant economic impact leaving general concern and uncertainty. Although vaccines have been developed and approved for use by various governments, the duration of the pandemic and its effects cannot be predicted with certainty. The impact of this coronavirus, and other epidemics and pandemics that may arise in the future, could affect the economies of many nations, individual companies and the market in general ways that cannot necessarily be foreseen at the present time.
BlackRock U.S. Carbon Transition Readiness ETF | Market Trading Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Market Trading Risk. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares (including through a trading halt), losses from trading in secondary markets, periods of high volatility, and disruptions in the process of creating and redeeming Fund shares. Any of these factors, among others, may lead to the Fund’s shares trading in the secondary market at a premium or discount to NAV or to the intraday value of the Fund’s portfolio holdings. If you buy Fund shares at a time when the market price is at a premium to NAV or sell Fund shares at a time when the market price is at a discount to NAV, you may pay significantly more or receive significantly less than the underlying value of the Fund shares.
BlackRock U.S. Carbon Transition Readiness ETF | Master Limited Partnerships Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Master Limited Partnerships Risk. The common units of an MLP are listed and traded on U.S. securities exchanges and their value fluctuates predominantly based on prevailing market conditions and the success of the MLP. Unlike owners of common stock of a corporation, owners of common units have limited voting rights and have no ability to annually elect directors. In the event of liquidation, common units have preference over subordinated units, but not over debt or preferred units, to the remaining assets of the MLP.
BlackRock U.S. Carbon Transition Readiness ETF | Mid Cap Securities Risk [Member]  
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Risk [Text Block] rr_RiskTextBlock
Mid Cap Securities Risk. The securities of mid cap companies generally trade in lower volumes and are generally subject to greater and less predictable price changes than the securities of larger capitalization companies.
BlackRock U.S. Carbon Transition Readiness ETF | Preferred Securities Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Preferred Securities Risk. Preferred securities may pay fixed or adjustable rates of return. Preferred securities are subject to issuer-specific and market risks applicable generally to equity securities. In addition, a company’s preferred securities generally pay dividends only after the company makes required payments to holders of its bonds and other debt. For this reason, the value of preferred securities will usually react more strongly than bonds and other debt to actual or perceived changes in the company’s financial condition or prospects. Preferred securities of smaller companies may be more vulnerable to adverse developments than preferred securities of larger companies.
BlackRock U.S. Carbon Transition Readiness ETF | REIT Investment Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
REIT Investment Risk. Investments in REITs involve unique risks. REITs may have limited financial resources, may trade less frequently and in limited volume, may engage in dilutive offerings of securities and may be more volatile than other securities. REIT issuers may also fail to maintain their exemptions from investment company registration or fail to qualify for the “dividends paid deduction” under the Internal Revenue Code of 1986, as amended, which allows REITs to reduce their corporate taxable income for dividends paid to their shareholders.
BlackRock U.S. Carbon Transition Readiness ETF | Small Fund Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Small Fund Risk. When the Fund’s size is small, the Fund may experience low trading volume and wide bid/ask spreads. In addition, the Fund may face the risk of being delisted if the Fund does not meet certain conditions of the listing exchange. Any resulting liquidation of the Fund could cause the Fund to incur elevated transaction costs for the Fund and negative tax consequences for its shareholders.
BlackRock U.S. Carbon Transition Readiness ETF | Technology Securities Risk [Member]  
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Risk [Text Block] rr_RiskTextBlock
Technology Securities Risk. Certain technology-related companies may face special risks that their
products or services may not prove to be commercially successful. Technology-related companies are also strongly affected by worldwide scientific or technological developments. As a result, their products may rapidly become obsolete. Such companies are also often subject to governmental regulation and may, therefore, be adversely affected by governmental policies. In addition, certain technology-related companies in which the Fund may invest may not currently be profitable and there can be no assurance that such companies will be profitable in the future.
BlackRock U.S. Carbon Transition Readiness ETF | Telecommunications Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Telecommunications Risk. The telecommunications industry is subject to governmental regulation and a greater price volatility than the overall market and the products and services of telecommunications companies may be subject to rapid obsolescence resulting from changing consumer tastes, intense competition, and strong market reactions to technological developments throughout the industry. Companies in the telecommunications sector may encounter distressed cash flows due to the need to commit substantial capital to meet increasing competition, particularly in formulating new products and services using new technology.
BlackRock U.S. Carbon Transition Readiness ETF | Warrants Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Warrants Risk. If the price of the underlying stock does not rise above the exercise price before the warrant expires, the warrant generally expires without any value and the Fund will lose any amount it paid for the warrant. Thus, investments in warrants may involve substantially more risk than investments in common stock. Warrants may trade in the same markets as their underlying stock; however, the price of the warrant does not necessarily move with the price of the underlying stock.
BlackRock U.S. Carbon Transition Readiness ETF | BlackRock U.S. Carbon Transition Readiness ETF  
Risk/Return: rr_RiskReturnAbstract  
Management Fees rr_ManagementFeesOverAssets 0.29% [1],[2]
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets none [3]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets none [2],[3]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.29%
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets (0.15%) [1],[2]
Total Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 0.14% [1],[2]
1 Year rr_ExpenseExampleYear01 $ 14
3 Years rr_ExpenseExampleYear03 69
5 Years rr_ExpenseExampleYear05 139
10 Years rr_ExpenseExampleYear10 $ 344
2022 rr_AnnualReturn2022 (20.00%) [4]
2023 rr_AnnualReturn2023 25.15% [4]
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2024
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 21.35%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel best
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2023
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 11.53%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel worst
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (16.83%)
One Year rr_AverageAnnualReturnYear01 25.15%
Since Fund Inception rr_AverageAnnualReturnSinceInception 6.36%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 06, 2021
BlackRock U.S. Carbon Transition Readiness ETF | Return After Taxes on Distributions | BlackRock U.S. Carbon Transition Readiness ETF  
Risk/Return: rr_RiskReturnAbstract  
One Year rr_AverageAnnualReturnYear01 24.67% [5]
Since Fund Inception rr_AverageAnnualReturnSinceInception 5.77% [5]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 06, 2021 [5]
BlackRock U.S. Carbon Transition Readiness ETF | Return After Taxes on Distributions and Sale of Fund Shares | BlackRock U.S. Carbon Transition Readiness ETF  
Risk/Return: rr_RiskReturnAbstract  
One Year rr_AverageAnnualReturnYear01 15.16% [5]
Since Fund Inception rr_AverageAnnualReturnSinceInception 4.77% [5]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 06, 2021 [5]
BlackRock U.S. Carbon Transition Readiness ETF | Russell 1000® Index (Gross Total Return) (Index returns do not reflect deductions for fees, expenses or taxes)  
Risk/Return: rr_RiskReturnAbstract  
One Year rr_AverageAnnualReturnYear01 26.53% [6]
Since Fund Inception rr_AverageAnnualReturnSinceInception 6.59% [6]
[1] As described in the “Management” section of the Fund’s prospectus beginning on page 17, BFA has contractually agreed to waive 0.15% of its management fee payable, through June 30, 2026.
[2] As described in the “Management” section of the Fund’s prospectus beginning on page 17, BFA has contractually agreed to waive a portion of its management fees in an amount equal to the aggregate Acquired Fund Fees and Expenses, if any, attributable to investments by the Fund in other equity and fixed-income mutual funds and exchange-traded funds (“ETFs”) advised by BFA or its affiliates through June 30, 2026. As described in the “Management” section of the Fund’s prospectus beginning on page 17, BFA has contractually agreed to waive a portion of its management fees in an amount equal to the aggregate Acquired Fund Fees and Expenses, if any, attributable to investments by the Fund in money market funds managed by BFA or its affiliates through June 30, 2026. The agreement (with respect to either waiver) may be terminated upon 90 days’ notice by a majority of the non-interested trustees of the Trust or by a vote of a majority of the outstanding voting securities of the Fund.
[3] The amount rounded to 0.00%.
[4] The Fund’s year-to-date return as of September 30, 2024 was 21.35%.
[5]
After-tax returns in the table above are calculated using the historical highest individual U.S. federal marginal income tax rates and do not reflect the impact of state or local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown, and after-tax returns shown are not relevant to tax-exempt investors or investors who hold shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts (“IRAs”). Fund returns after taxes on distributions and sales of Fund shares are calculated assuming that an investor has sufficient capital gains of the same character from other investments to offset any capital losses from the sale of Fund shares. As a result, Fund returns after taxes on distributions and sales of Fund shares may exceed Fund returns before taxes and/or returns after taxes on distributions.
[6]
The Russell 1000® Index measures the performance of the large-cap segment of the U.S. equity universe. The Russell 1000® Index is a subset of the Russell 3000® Index which is designed to represent approximately 98% of the investable U.S. equity market.