Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	iShares U.S. ETF Trust
Prospectus Date	rr_ProspectusDate	Dec. 09, 2013
iShares Liquidity Income ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	iSHARES® LIQUIDITY INCOME ETF Ticker: ICSH                 Stock Exchange: BATS
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The iShares Liquidity Income ETF (the “Fund”) seeks to provide current income consistent with preservation of capital.
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. 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.
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:
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 a portfolio of U.S. dollar-denominated investment-grade fixed- and floating-rate debt securities that are rated BBB- or higher by Standard & Poor’s Ratings Services and/or Fitch Ratings, Inc. (“Fitch”), or Baa3 or higher by Moody’s Investors Service, Inc. (“Moody’s”), or, if unrated, determined by BFA to be of equivalent quality. Under normal circumstances, the Fund will invest primarily in fixed- and floating-rate securities maturing in three years or less. Short-term investments (generally, securities with original maturities of one year or less) held by the Fund will carry a rating in one of the highest two rating categories of at least one nationally recognized statistical ratings organization (“NRSRO”) (e.g., A-2, P-2 or F2 or better by Standard & Poor’s Ratings Services, Moody’s or Fitch, respectively), or if such investments are unrated, determined to be of comparable quality by BFA, at the time of investment. The Fund may invest in corporate and U.S. and non-U.S. government bonds, agency securities, instruments of non-U.S. issuers, privately-issued securities, asset-backed and mortgage-backed securities, structured securities, municipal bonds, repurchase agreements, money market instruments and investment companies (including investment companies advised by BFA or its affiliates). The Fund invests a significant portion of its assets in securities issued by financial institutions, such as banks, broker-dealers and insurance companies. Under normal circumstances, the dollar-weighted average life of the Fund’s portfolio is expected to be one year or less, as calculated by BFA. The Fund will also seek to maintain a dollar-weighted average maturity that is less than 180 days. “Dollar-weighted average life,” or “WAL,” is the weighted average of the times when principal is to be repaid. “Dollar-weighted average maturity,” or “WAM,” is calculated by taking the average length of time to maturity (fixed-rate) or the next interest rate reset (floating-rate) for each underlying instrument held by the Fund, weighted according to the relative holdings per instrument. The Fund is an actively managed exchange-traded fund (“ETF”) that does not seek to replicate the performance of a specified index. The Fund may have a higher degree of portfolio turnover than funds that seek to replicate the performance of an index. The Fund is not a money market fund and does not seek to maintain a stable net asset value of $1.00 per share. Please see the Fund's Statement of Additional Information (“SAI”) for further information. 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. Agency Debt Risk. The Fund invests in unsecured bonds or debentures issued by government agencies, including the Federal National Mortgage Association (“Fannie Mae”) and the Federal Home Loan Mortgage Corporation (“Freddie Mac”). Bonds or debentures issued by government agencies are generally backed only by the general creditworthiness and reputation of the government agency issuing the bond or debenture and are not backed by the full faith and credit of the U.S. government. As a result, there is uncertainty as to the current status of many obligations of Fannie Mae, Freddie Mac and other agencies that are placed under conservatorship of the federal government. Asset-Backed and Mortgage-Backed Securities Risk. Asset-backed and mortgage-backed securities (residential and commercial) represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. Asset-backed and mortgage-backed securities are subject to credit, interest rate, call, extension, valuation and liquidity risk. These securities, in most cases, are not backed by the full faith and credit of the U.S. government and are subject to the risk of default on the underlying asset or mortgage, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain asset-backed and mortgage-backed securities. Asset Class Risk. Securities in the Fund's portfolio may underperform in comparison to the general securities markets or other asset classes. Call Risk. During periods of falling interest rates, an issuer of a callable bond held by the Fund may “call” or repay the security before its stated maturity, and the Fund may have to reinvest the proceeds at lower interest rates, resulting in a decline in the Fund's income. Credit Risk. Debt issuers and other counterparties may not honor their obligations or may have their debt downgraded by ratings agencies. Extension Risk. During periods of rising interest rates, certain debt obligations will be paid off substantially more slowly than originally anticipated and the value of those securities may fall sharply, resulting in a decline in the Fund’s income and potentially in the value of the Fund’s investments. 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. Floating Rate Notes Risk. Securities with floating or variable interest rates can be less sensitive to interest rate changes than securities with fixed interest rates, but may decline in value if their coupon rates do not reset as high, or as quickly, as comparable market interest rates, and generally carry lower yields than fixed notes of the same maturity. Although floating rate notes are less sensitive to interest rate risk than fixed rate securities, they are subject to credit and default risk, which could impair their value. 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. Income Risk. The Fund’s income may decline when interest rates fall because the Fund may hold a significant portion of short duration securities and/or securities that have floating or variable interest rates. The Fund’s income may decline because the Fund invests in lower yielding bonds, and as the bonds in its portfolio mature, the Fund needs to purchase additional bonds. Interest Rate Risk. An increase in interest rates may cause the value of fixed-income securities held by the Fund to decline. 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. 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. Municipal Securities Risk. Municipal securities can be significantly affected by political or economic changes as well as uncertainties in the municipal market related to taxation, legislative changes or the rights of municipal security holders. Municipal securities backed by current or anticipated revenues from a specific project or specific assets can be negatively affected by the inability to collect revenues for the project or from the assets. Non-U.S. Issuers Risk. Securities issued by non-U.S. issuers carry different risks from securities issued by U.S. issuers. These include differences in accounting, auditing and financial reporting standards, the possibility of expropriation or confiscatory taxation, adverse changes in investment or exchange control regulations, political instability, regulatory and economic differences, and potential restrictions on the flow of international capital. The Fund is specifically exposed to European Economic Risk and North American Economic Risk. Not a Money Market Fund. The Fund is not a money market fund and is not subject to the strict rules that govern the quality, maturity, liquidity and other features of securities that money market funds may purchase. Under normal circumstances, the Fund’s investments may be more susceptible than a money market fund is to credit risk, interest rate risk, valuation risk and other risks relevant to the Fund’s investments. The Fund does not seek to maintain a stable net asset value of $1.00 per share. Privately-Issued Securities Risk. The Fund will invest in privately-issued securities, including those that are normally purchased pursuant to Rule 144A or Regulation S promulgated under the Securities Act of 1933, as amended (the “1933 Act”). Privately-issued securities are securities that have not been registered under the 1933 Act and as a result are subject to legal restrictions on resale. Privately-issued securities are not traded on established markets and may be illiquid, difficult to value and subject to wide fluctuations in value. Delay or difficulty in selling such securities may result in a loss to the Fund. Repurchase Agreement Risk. A repurchase agreement is an instrument under which the purchaser (i.e., the Fund) acquires a security and the seller agrees, at the time of the sale, to repurchase the security at a mutually agreed upon time and price. Repurchase agreements may be construed to be collateralized loans by the purchaser to the seller secured by the securities transferred to the purchaser. If a repurchase agreement is construed to be a collateralized loan, the underlying securities will not be considered to be owned by the Fund but only to constitute collateral for the seller’s obligation to pay the repurchase price. If the seller defaults on its obligation under the agreement, the Fund may suffer delays and incur costs or lose money in exercising its rights under the agreement. If the seller fails to repurchase the security and the market value of the security declines, the Fund may lose money. 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. 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. Sovereign and Quasi-Sovereign Obligations Risk. The Fund may invest in securities issued by or guaranteed by sovereign governments, which may be unable or unwilling to repay principal or interest when due. In times of economic uncertainty, the prices of these securities may be more volatile than those of corporate debt obligations or of other government debt obligations. Telecommunications Sector Risk. Companies in the telecommunications sector may be affected by industry competition, substantial capital requirements, government regulation and obsolescence of telecommunications products and services due to technological advancement. U.S. Treasury Obligations Risk. U.S. Treasury obligations may differ from other securities in their interest rates, maturities, times of issuance and other characteristics. Similar to other issuers, changes to the financial condition or credit rating of the U.S. government may cause the value of the Fund's U.S. Treasury obligations to decline. Valuation Risk. The sale price the Fund could receive for a security may differ from the Fund's valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund's portfolio may change on days when shareholders will not be able to purchase or sell the Fund's shares.
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 Liquidity Income ETF | iShares Liquidity Income ETF
Risk/Return:	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.18%
Distribution and Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	none
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.18%
1 Year	rr_ExpenseExampleYear01	$ 18
3 Years	rr_ExpenseExampleYear03	$ 58