Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	iShares U.S. ETF Trust
Prospectus Date	rr_ProspectusDate	Dec. 01, 2013
iShares Enhanced U.S. Small-Cap ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	iSHARES® ENHANCED U.S. SMALL-CAP ETF Ticker: IESM                   Stock Exchange: NYSE Arca
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The iShares Enhanced U.S. Small-Cap ETF (the “Fund”) seeks long-term capital appreciation.
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 own shares of the Fund. The investment advisory agreement between iShares U.S. ETF Trust (the “Trust”) and BlackRock Fund Advisors (“BFA”) (the “Investment Advisory Agreement”) provides that BFA will pay all operating expenses of the Fund, except interest expenses, taxes, brokerage expenses, future distribution fees or expenses, and extraordinary expenses. The Fund will also pay Acquired Fund Fees and Expenses. “Acquired Fund Fees and Expenses” reflect the Fund's pro rata share of the fees and expenses incurred by investing in other investment companies. Acquired Fund Fees and Expenses are based on an estimate of the Fund's allocation to other investment companies for the current fiscal year. The impact of Acquired Fund Fees and Expenses is included in the total returns of the Fund. Acquired Fund Fees and Expenses are not used to calculate the Fund's net asset value per share (“NAV”) and are not included in the calculation of the ratio of expenses to average net assets shown in the Financial Highlights section of the Fund's prospectus (the “Prospectus”). You may also incur usual and customary brokerage commissions when buying or selling shares of the Fund, which are not reflected in the Example that follows:
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (ongoing expenses that you pay each year as a percentage of the value of your investments)
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 Annual Fund Operating Expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 9% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	9.00%
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	You may also incur usual and customary brokerage commissions when buying or selling shares of the Fund, which are not reflected in the Example that follows:
Acquired Fund Fees and Expenses, Based on Estimates [Text]	rr_AcquiredFundFeesAndExpensesBasedOnEstimates	Acquired Fund Fees and Expenses are based on an estimate of the Fund's allocation to other investment companies for the current fiscal year.
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Acquired Fund Fees and Expenses are not used to calculate the Fund's net asset value per share (“NAV”) and are not included in the calculation of the ratio of expenses to average net assets shown in the Financial Highlights section of the Fund's prospectus (the “Prospectus”).
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 achieve its investment objective by investing, under normal circumstances, at least 80% of its net assets in equity securities of U.S. small-capitalization issuers. The Fund is an actively managed exchange-traded fund ("ETF") that does not seek to replicate the performance of a specified index. The Fund will seek to invest in strategic U.S. small-capitalization stocks with targeted investment characteristics. BFA utilizes a proprietary investment process to assemble an investment portfolio from a defined group of U.S. small-capitalization stocks based on certain quantitative investment characteristics, including, but not limited to, cash earnings, earnings variability, leverage, price-to-book ratio and market capitalization. Companies in the universe of U.S. small-capitalization securities include consumer discretionary, financials and information technology companies, and may change over time. The Fund may have a higher portfolio turnover than funds that seek to replicate the performance of an index. The Fund may lend securities representing up to one-third of the value of the Fund's total assets (including the value of the collateral received).
Risk [Heading]	rr_RiskHeading	Summary of Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	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. The Fund is subject to the principal risks noted below, any of which may adversely affect the Fund's net asset value per share ("NAV"), trading price, yield, total return and ability to meet its investment objective. Unlike many ETFs, the Fund is not an index-based ETF. Asset Class Risk. Securities in the Fund's portfolio may underperform in comparison to the general securities markets, a particular securities market, or other asset classes. Consumer Discretionary Sector Risk. The consumer discretionary sector may be affected by changes in domestic and international economies, exchange and interest rates, competition, consumers' disposable income and consumer preferences, social trends and marketing campaigns. Equity Securities Risk. Equity securities are subject to changes in value and their values may be more volatile than those of other asset classes. Factor Risk. The Fund seeks to provide exposure to U.S. small-capitalization stocks based on certain quantitative investment characteristics ("factors"), including, but not limited to, cash earnings, earnings variability, leverage, price-to-book ratio and market capitalization. There can be no assurance that exposure to such investment factors will enhance the Fund's performance over time. It is expected that exposure to such investment factors will detract from performance in some market environments, perhaps for extended periods. In such circumstances, BFA will seek to maintain exposure to the targeted investment factors and will not adjust the Fund's investment process to target different factors. Financials Sector Risk. Performance of companies in the financials sector may be adversely impacted by many factors, including, among others, government regulations, economic conditions, credit rating downgrades, changes in interest rates, and decreased liquidity in credit markets. This sector has experienced significant losses in the recent past, and the impact of more stringent capital requirements and of recent or future regulation on any individual financial company or on the sector as a whole cannot be predicted. High Portfolio Turnover Risk. The Fund may engage in active and frequent trading of its portfolio securities. High portfolio turnover (higher than 100%) may result in increased transaction costs to the Fund, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities, as well as possible increased taxable distributions. Information Technology Sector Risk. Information technology companies face intense competition and potentially rapid product obsolescence. They are also heavily dependent on intellectual property rights and may be adversely affected by loss or impairment of those rights. Investment Exposure Risk. The Fund is designed to consider targeted investment factors. BFA will not attempt to consider factors outside the targeted investment factors or take defensive positions under any market conditions, including declining markets. 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. There is no guarantee that an issuer that paid dividends in the past will continue to do so in the future or will continue paying dividends at the same level. Management Risk. The Fund is subject to management risk, which is the risk that the investment process, techniques and risk analyses applied by BFA will not produce the desired results, and that securities selected by BFA may underperform the market or any relevant benchmark. In addition, legislative, regulatory, or tax developments may affect the investment techniques available to BFA in connection with managing the Fund and may also adversely affect the ability of the Fund to achieve its investment objective. Market Risk. The Fund could lose money over short periods due to short-term market movements and over longer periods during market downturns. Market Trading Risk. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. Unlike some ETFs that track specific indexes, the Fund does not seek to replicate the performance of a specified index. Index-based ETFs have generally traded at prices that closely correspond to NAV. Given the high level of transparency of the Fund's holdings, BFA believes that the trading experience of the Fund should be similar to that of index-based ETFs. However, ETFs that do not seek to replicate the performance of a specified index have a limited trading history and, therefore, there can be no assurance as to whether, and/or the extent to which, the Fund's shares will trade at premiums or discounts to NAV. ANY OF THESE FACTORS, AMONG OTHERS, MAY LEAD TO THE FUND'S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. Securities Lending Risk. The Fund may engage in securities lending. Securities lending involves the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of the collateral provided for loaned securities or a decline in the value of any investments made with cash collateral. These events could also trigger adverse tax consequences for the Fund. Small-Capitalization Companies Risk. Compared to mid- and large-capitalization companies, small-capitalization companies may be less stable and more susceptible to adverse developments, and their securities may be more volatile and less liquid. Value Securities Risk. Securities issued by companies that may be perceived as undervalued may fail to appreciate for long periods of time and may never realize their full potential value.
Risk Lose Money [Text]	rr_RiskLoseMoney	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.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	As of the date of the Prospectus, the Fund has been in operation for less than one full calendar year and therefore does not report its performance information.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	As of the date of the Prospectus, the Fund has been in operation for less than one full calendar year and therefore does not report its performance information.
iShares Enhanced U.S. Small-Cap ETF | iShares Enhanced U.S. Small-Cap ETF
Risk/Return:	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.35%
Distribution and Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	none
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.36%
1 Year	rr_ExpenseExampleYear01	$ 37
3 Years	rr_ExpenseExampleYear03	$ 116