| Label | Element | Value | ||
|---|---|---|---|---|
| iShares Prime Money Market ETF | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk/Return [Heading] | rr_RiskReturnHeading | iSHARES PRIME MONEY MARKET ETFTicker: PMMF Stock Exchange: NYSE Arca | ||
| Objective [Heading] | rr_ObjectiveHeading | Investment Objective | ||
| Objective, Primary [Text Block] | rr_ObjectivePrimaryTextBlock | The iShares Prime Money Market ETF (the “Fund”) seeks as high a level of current income as is consistent with liquidity and stability of principal.
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| 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”) (the “Investment Advisory Agreement”) 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. 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.
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| 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) | ||
| Other Expenses, New Fund, Based on Estimates [Text] | rr_OtherExpensesNewFundBasedOnEstimates | Other Expenses are based on estimated amounts for the Fund’s current fiscal year. Amount rounds to 0.00%. | ||
| 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:
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| 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, in a broad range of U.S. dollar-denominated money market instruments, including government, U.S. and foreign bank, and commercial obligations and repurchase agreements. The Fund invests in securities maturing in 397 days or less (with certain exceptions) and the portfolio will have a dollar-weighted average maturity of 60 days or less and a dollar-weighted average life of 120 days or less. In addition, the Fund may invest in mortgage- and asset-backed securities, short-term obligations issued by or on behalf of states, territories and possessions of the United States, the District of Columbia, and their respective authorities, agencies, instrumentalities and political subdivisions and derivative securities such as tender option bonds, beneficial interests in municipal trust certificates and partnership trusts. The Fund may also invest in variable and floating rate instruments, and transact in securities on a when-issued, delayed delivery or forward commitment basis. The Fund’s Board of Trustees (the “Board”) has determined that the Fund will qualify as a “money market fund” pursuant to Rule 2a‑7 under the Investment Company Act of 1940, as amended (“Rule 2a‑7”). The securities purchased by the Fund are subject to the quality, diversification, and other requirements of Rule 2a‑7, and other rules of the Securities and Exchange Commission (“SEC”). Unlike a traditional money market fund, the Fund operates as an exchange traded fund (“ETF”). As an ETF, the Fund’s shares will be traded on NYSE Arca (“NYSE Arca”) and will generally fluctuate in accordance with changes in net asset value (“NAV”) per share as well as the relative supply of, and demand for, shares on NYSE Arca. You could lose money by investing in the Fund. The Fund is an actively managed ETF that does not seek to replicate the performance of a specified index.
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| Risk [Heading] | rr_RiskHeading | Summary of Principal Risks | ||
| Bar Chart and Performance Table [Heading] | rr_BarChartAndPerformanceTableHeading | Performance Information | ||
| Performance Narrative [Text Block] | rr_PerformanceNarrativeTextBlock | Because the Fund has not commenced operations as of the date of this Prospectus, it does not have performance information an investor would find useful in evaluating the risks of investing in the Fund.
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| Performance One Year or Less [Text] | rr_PerformanceOneYearOrLess | Because the Fund has not commenced operations as of the date of this Prospectus, it does not have performance information an investor would find useful in evaluating the risks of investing in the Fund. | ||
| iShares Prime Money Market 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. | ||
| iShares Prime Money Market ETF | Risk Money Market Fund Price Fluctuates [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | Because the share price and NAV of the Fund will fluctuate, when shares are sold (or redeemed, in the case of an Authorized Participant), they may be worth more or less than what was originally paid for them. | ||
| iShares Prime Money Market ETF | Risk Money Market Fund Sponsor May Not Provide Support [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | The Fund’s sponsor is not required to reimburse the Fund for losses, and you should not expect that the sponsor will provide financial support to the Fund at any time, including during periods of market stress. | ||
| iShares Prime Money Market ETF | Risk Not Insured Depository Institution [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | An investment in the Fund is not a bank account and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. | ||
| iShares Prime Money Market ETF | Credit Risks [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | Credit Risk. Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will be unable or unwilling to make timely payments of interest and principal when due or otherwise honor their obligations. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also adversely affect the value of the Fund’s investment in that issuer.
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| iShares Prime Money Market ETF | Interest Rate Risks [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | Interest Rate Risk. Interest rate risk is the risk that the value of a debt security may fall when interest rates rise. In general, the market price of debt securities with longer maturities will go up or down more in response to changes in interest rates than the market price of shorter-term securities. Due to fluctuations in interest rates, the market value of such securities may vary during the period shareholders own shares of the Fund. Very low or negative interest rates may magnify interest rate risk. During periods of very low or negative interest rates, the Fund may be unable to maintain positive returns or pay dividends to Fund shareholders. The Fund may be subject to a greater risk of rising interest rates during a period of historically low interest rates. Changing interest rates may have unpredictable effects on markets, may result in heightened market volatility, and may detract from the Fund’s ability to achieve its investment objective.
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| iShares Prime Money Market ETF | Repurchase Agreements Risk [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | Repurchase Agreements Risk. If the other party to a repurchase agreement 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.
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| iShares Prime Money Market 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 that you may lose money.
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| iShares Prime Money Market ETF | Assets Under Management AUM Risk [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | Assets Under Management (AUM) Risk. From time to time, an Authorized Participant (as defined below in Authorized Participant Concentration Risk), 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.
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| iShares Prime Money Market ETF | Authorized Participant Concentration Risk [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | Authorized Participant Concentration Risk. An “Authorized Participant” is a member or participant of a clearing agency registered with the SEC, which has a written agreement with the Fund or one of its service providers that allows the Authorized Participant to place orders for the purchase and redemption of creation units (“Creation Units”). 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.
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| iShares Prime Money Market ETF | Cash Transactions Risk [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | Cash Transactions Risk. The Fund expects to effect all of its creations and redemptions for cash, rather than in‑kind securities. As a result, the Fund may have to sell portfolio securities at inopportune times in order to obtain the cash needed to meet redemption orders. This may cause the Fund to sell a security and recognize a capital gain or loss that might not have been incurred if it had made a redemption in‑kind. The use of cash creations and redemptions may also cause the Fund’s shares to trade in the market at wider bid‑ask spreads or greater premiums or discounts to the Fund’s NAV.
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| iShares Prime Money Market ETF | Discretionary Liquidity Fee Risk [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | Discretionary Liquidity Fee Risk. The Board, or its delegate, has discretion to impose a liquidity fee of up to 2% upon the redemption of shares if the Board or its delegate determines that is in the best interest of the Fund. Accordingly, redemptions by Authorized Participants may be subject to a discretionary liquidity fee when an Authorized Participant redeems shares, which may impact the Fund’s price on NYSE Arca. A potential liquidity fee, even if not imposed, may also impact the Fund’s share price on NYSE Arca. Investors trading on NYSE Arca will not be directly subject to the discretionary liquidity fee.
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| iShares Prime Money Market ETF | Extension Risk [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | Extension Risk. When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these securities to fall.
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| iShares Prime Money Market ETF | Foreign Exposure Risk [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | Foreign Exposure Risk. Securities issued or supported by foreign entities, including foreign banks and corporations, may involve additional risks and considerations. Extensive public information about the foreign issuer may not be available, and unfavorable political, economic or governmental developments in the foreign country involved could affect the payment of principal and interest.
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| iShares Prime Money Market ETF | Income Risk [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | Income Risk. Income risk is the risk that the Fund’s yield will vary as short-term securities in its portfolio mature and the proceeds are reinvested in securities with different interest rates.
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| iShares Prime Money Market 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.
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| iShares Prime Money Market 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. These large redemptions may also force the Fund to sell portfolio securities or other assets 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.
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| iShares Prime Money Market ETF | Mandatory Liquidity Fee Risk [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | Mandatory Liquidity Fee Risk. The Board, or its delegate, must impose a mandatory liquidity fee upon all shares redeemed if the Fund’s net redemptions on any business day exceed 5% of the Fund’s net assets, unless the liquidity costs are de minimis. Accordingly, redemptions by Authorized Participants may be subject to a mandatory liquidity fee at certain times, which may impact the Fund’s price on NYSE Arca. A potential liquidity fee, even if not imposed, may also impact the Fund’s share price on NYSE Arca. Investors trading on NYSE Arca will not be directly subject to the mandatory liquidity fee.
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| iShares Prime Money Market 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.
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| iShares Prime Money Market ETF | Mortgage and Asset Backed Securities Risks [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | Mortgage- and Asset-Backed Securities Risks. Mortgage- and asset-backed securities represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. Mortgage- and asset-backed securities are subject to credit, interest rate, prepayment and extension risks. These securities also are subject to risk of default on the underlying mortgage or asset, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain mortgage-backed securities.
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| iShares Prime Money Market ETF | Prepayment Risks [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | Prepayment Risk. When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields.
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| iShares Prime Money Market 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.
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| iShares Prime Money Market 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.
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| iShares Prime Money Market ETF | Treasury Obligations Risk [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | Treasury Obligations Risk. Direct obligations of the U.S. Treasury have historically involved little risk of loss of principal if held to maturity. However, due to fluctuations in interest rates, the market value of such securities may vary during the period shareholders own shares of the Fund. In addition, notwithstanding that U.S. Treasury obligations are backed by the full faith and credit of the United States, circumstances could arise that could prevent the timely payment of interest or principal, such as reaching the legislative “debt ceiling.” Such non‑payment could result in losses to the Fund and substantial negative consequences for the U.S. economy and the global financial system.
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| iShares Prime Money Market ETF | U S Government Obligations Risk [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | U.S. Government Obligations Risk. Certain securities in which the Fund may invest, including securities issued by certain U.S. Government agencies and U.S. Government sponsored enterprises, are not guaranteed by the U.S. Government or supported by the full faith and credit of the United States. In addition, circumstances could arise that could prevent the timely payment of interest or principal on U.S. Government obligations, such as reaching the legislative “debt ceiling.” Such non‑payment could result in losses to the Fund and substantial negative consequences for the U.S. economy and the global financial system.
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| iShares Prime Money Market ETF | Variable and Floating Rate Instrument Risk [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | Variable and Floating Rate Instrument Risk. Variable and floating rate securities provide for periodic adjustment in the interest rate paid on the securities. 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 securities of the same maturity. These securities will not generally increase in value if interest rates decline. A decline in interest rates may result in a reduction in income received from variable and floating rate securities held by the Fund and may adversely affect the value of the Fund’s shares. These securities may be subject to greater illiquidity risk than other fixed income securities, meaning the absence of an active market for these securities could make it difficult for the Fund to dispose of them at any given time. Floating rate securities generally are subject to legal or contractual restrictions on resale, may trade infrequently, and their value may be impaired when the Fund needs to liquidate such loans. Benchmark interest rates may not accurately track market interest rates. Although floating rate securities are less sensitive to interest rate risk than fixed-rate securities, they are subject to credit risk and default risk, which could impair their value.
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| iShares Prime Money Market ETF | When Issued and Delayed Delivery Securities and Forward Commitments Risk [Member] | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Risk [Text Block] | rr_RiskTextBlock | When-Issued and Delayed Delivery Securities and Forward Commitments Risk. When-issued and delayed delivery securities and forward commitments involve the risk that the security the Fund buys will lose value prior to its delivery. There also is the risk that the security will not be issued or that the other party to the transaction will not meet its obligation. If this occurs, the Fund may lose both the investment opportunity for the assets it set aside to pay for the security and any gain in the security’s price.
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| iShares Prime Money Market ETF | iShares Prime Money Market ETF | ||||
| Risk/Return: | rr_RiskReturnAbstract | |||
| Management Fees | rr_ManagementFeesOverAssets | 0.20% | ||
| Distribution and Service (12b‑1) Fees | rr_DistributionAndService12b1FeesOverAssets | none | ||
| Other Expenses | rr_OtherExpensesOverAssets | none | [1] | |
| Total Annual Fund Operating Expenses | rr_ExpensesOverAssets | 0.20% | ||
| 1 Year | rr_ExpenseExampleYear01 | $ 20 | ||
| 3 Years | rr_ExpenseExampleYear03 | $ 64 | ||
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