Objective, Primary [Text Block]

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Overview Key Facts About iShares Short-Term TIPS Bond Index Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

rr_ObjectivePrimaryTextBlock

The investment objective of iShares Short-Term TIPS Bond Index Fund (the “Fund”), a series of BlackRock FundsSM (the “Trust”), is to seek to track the investment results of an index composed of U.S. 0-5 Year Treasury Inflation-Protected Securities (“TIPS”).

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to your financial professional or your selected securities dealer, broker, investment adviser, service provider or industry professional (including BlackRock Advisors, LLC (“BlackRock”) and its affiliates) (each, a “Financial Intermediary”), which are not reflected in the table and example below.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

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 pays 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 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 18% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

18.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example:

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem 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 of the Fund

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund seeks to track the investment results of the Bloomberg U.S. Treasury Inflation-Protected Securities (TIPS) 0-5 Years Index (Series-L) (the “Underlying Index”), which measures the performance of inflation-protected public obligations of the U.S. Treasury that have a remaining maturity of less than five years. Inflation-protected public obligations of the U.S. Treasury, commonly known as “TIPS,” are securities issued by the U.S. Treasury that are designed to provide inflation protection to investors. TIPS are income-generating instruments whose interest and principal payments are adjusted for inflation — a sustained increase in prices that erodes the purchasing power of money. The inflation adjustment, which is typically applied monthly to the principal of the bond, follows a designated inflation index, the consumer price index (“CPI”), and TIPS’ principal payments are adjusted according to changes in the CPI. A fixed coupon rate is applied to the inflation-adjusted principal so that as inflation rises, both the principal value and the interest payments increase. This can provide investors with a hedge against inflation, as it helps preserve the purchasing power of an investment. Because of this inflation adjustment feature, inflation-protected bonds typically have lower yields than conventional fixed-rate bonds. If there is deflation, the principal value of an inflation-linked security will be adjusted downward, and consequently the interest payments (calculated with respect to a smaller principal amount) will be reduced. During periods of deflation, low inflation or no inflation, a conventional bond may perform better than inflation-linked securities.

The Underlying Index includes all publicly-issued U.S. Treasury inflation-protected securities that have less than five years remaining to maturity, are rated investment-grade and have $250 million or more of outstanding face value. In addition, the securities in the Underlying Index must be denominated in U.S. dollars and have a notional coupon that is fixed-rate or zero. The Underlying Index is market capitalization-weighted and the securities in the Underlying Index are updated on the last calendar day of each month.

BlackRock uses a representative sampling indexing strategy to manage the Fund. “Representative sampling” is an indexing strategy that involves investing in a representative sample of securities that collectively has an investment profile similar to that of the Underlying Index. The securities selected are expected to have, in the aggregate, investment characteristics (based on factors such as market capitalization and industry weightings), fundamental characteristics (such as return variability and yield) and liquidity measures similar to those of the Underlying Index. The Fund may or may not hold all of the securities in the Underlying Index.

The Fund generally invests at least 90% of its assets, plus the amount of any borrowing for investment purposes, in securities of the Underlying Index. From time to time when conditions warrant, however, the Fund may invest at least 80% of its assets in securities of the Underlying Index. The Fund may invest a portion of the remainder of its assets in securities not included in the Underlying Index, but which BlackRock believes will help the Fund track the Underlying Index.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing in the Fund

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 for the periods since inception and provides some indication of the risks of investing in the Fund. The table compares the Fund’s performance to that of the ICE BofA U.S. Broad Market Index and the Bloomberg U.S. Treasury Inflation-Protected Securities (TIPS) 0-5 Years Index (Series-L). The Bloomberg U.S. Treasury Inflation-Protected Securities (TIPS) 0-5 Years Index (Series L) is relevant to the Fund because it has characteristics similar to the Fund’s investment strategies. 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. The table includes all applicable fees. If BlackRock and its affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund’s returns would have been lower. Updated information on the Fund’s performance, including its current net asset value, can be obtained by visiting www.blackrock.com or can be obtained by phone at (800) 882-0052.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The information shows you how the Fund’s performance has varied for the periods since inception and provides some indication of the risks of investing in the Fund.

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

The table compares the Fund’s performance to that of the ICE BofA U.S. Broad Market Index and the Bloomberg U.S. Treasury Inflation-Protected Securities (TIPS) 0-5 Years Index (Series-L). The Bloomberg U.S. Treasury Inflation-Protected Securities (TIPS) 0-5 Years Index (Series L) is relevant to the Fund because it has characteristics similar to the Fund’s investment strategies.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

(800) 882-0052

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

Investor A Shares ANNUAL TOTAL RETURNS iShares Short-Term TIPS Bond Index Fund As of 12/31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

During the periods shown in the bar chart, the highest return for a quarter was 2.50% (quarter ended September 30, 2024) and the lowest return for a quarter was -2.76% (quarter ended September 30, 2022).

Performance Table Heading

rr_PerformanceTableHeading

For the periods ended 12/31/24Average Annual Total Returns

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Investor A Shares only. The after-tax returns for Institutional Shares will vary.

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Investor A Shares only. The after-tax returns for Institutional Shares will vary.

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | Risk Lose Money [Member]

rr_RiskReturnAbstract

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | U S Treasury Obligations Risk [Member]

rr_RiskTextBlock

You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments.

rr_RiskReturnAbstract

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | Inflation Indexed Bonds Risk [Member]

rr_RiskTextBlock

◼

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 and may provide relatively lower returns than those of other securities. 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.

rr_RiskReturnAbstract

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | Index Related Risk [Member]

rr_RiskTextBlock

◼

Inflation-Indexed Bonds Risk — The principal value of an investment is not protected or otherwise guaranteed by virtue of the Fund’s investments in inflation-indexed bonds.

Inflation-indexed bonds are fixed-income securities whose principal value is periodically adjusted according to the rate of inflation. If the index measuring inflation falls, the principal value of inflation-indexed bonds will be adjusted

downward, and consequently the interest payable on these securities (calculated with respect to a smaller principal amount) will be reduced.

Repayment of the original bond principal upon maturity (as adjusted for inflation) is guaranteed in the case of U.S. Treasury inflation-indexed bonds. For bonds that do not provide a similar guarantee, the adjusted principal value of the bond repaid at maturity may be less than the original principal value.

The value of inflation-indexed bonds is expected to change in response to changes in real interest rates. Real interest rates are tied to the relationship between nominal interest rates and the rate of inflation. If nominal interest rates increase at a faster rate than inflation, real interest rates may rise, leading to a decrease in value of inflation-indexed bonds. Short-term increases in inflation may lead to a decline in value. Any increase in the principal amount of an inflation-indexed bond will be considered taxable ordinary income, even though investors do not receive their principal until maturity.

Periodic adjustments for inflation to the principal amount of an inflation-indexed bond may give rise to original issue discount, which will be includable in the Fund’s gross income. Due to original issue discount, the Fund may be required to make annual distributions to shareholders that exceed the cash received, which may cause the Fund to liquidate certain investments when it is not advantageous to do so. Also, if the principal value of an inflation-indexed bond is adjusted downward due to deflation, amounts previously distributed in the taxable year may be characterized in some circumstances as a return of capital.

rr_RiskReturnAbstract

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | Passive Investment Risk [Member]

rr_RiskTextBlock

◼

Index-Related Risk — The index provider may rely on various sources of information to assess the criteria of components of the Underlying Index, including information that may be based on assumptions and estimates. Neither the Fund nor BlackRock can offer assurances that the index provider’s methodology or sources of information will provide an accurate assessment of included components. Errors in index data, index computations or the construction of the Underlying Index in accordance with its methodology may occur, and the index provider may not identify or correct them promptly or at all, which may have an adverse impact on the Fund and its shareholders. Unusual market conditions or other unforeseen circumstances (such as natural disasters, political unrest or war) may impact the index provider or a third-party data provider and could cause the index provider to postpone a scheduled rebalance. This could cause the Underlying Index to vary from its normal or expected composition.

rr_RiskReturnAbstract

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | Tracking Error Risk [Member]

rr_RiskTextBlock

◼

Passive Investment Risk — Because BlackRock does not select individual companies in the index that the Fund tracks, the Fund may hold securities of companies that present risks that an investment adviser researching individual securities might seek to avoid.

rr_RiskReturnAbstract

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | Asset Class Risk [Member]

rr_RiskTextBlock

◼

Tracking Error Risk — The Fund is subject to the risk of “tracking error,” which is the divergence of the Fund’s performance from that of the Underlying Index. Tracking error may occur due to a number of factors, including differences between the securities and other assets held in the Fund’s portfolio and those included in the Underlying Index; differences in the timing and methodologies used to value securities and other assets; transaction costs and other expenses incurred by the Fund that the Underlying Index does not incur; the Fund’s holding of uninvested cash; differences in the timing of the accrual or the valuation of dividends or interest received by the Fund or distributions paid to Fund shareholders; tax gains or losses; the requirements for the Fund to maintain pass-through tax treatment; portfolio transactions carried out to minimize the distribution of capital gains to shareholders; changes to the Underlying Index, such as during a rebalancing or reconstitution; and impacts to the Fund of complying with certain regulatory requirements or limits. A fund that tracks an index composed of a large number of securities or other assets may experience greater tracking error than a fund that tracks a more narrow index. Tracking error risk may be heightened during times of increased market volatility or other unusual market conditions.

rr_RiskReturnAbstract

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | Income Risk [Member]

rr_RiskTextBlock

◼

Asset Class Risk — The securities and other assets or financial instruments in the Underlying Index or in the Fund’s portfolio may underperform in comparison to financial markets generally, a particular financial market, another index, or other asset classes.

rr_RiskReturnAbstract

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | Interest Rate Risks [Member]

rr_RiskTextBlock

◼

Income Risk— The Fund’s income may decline due to a decline in inflation, deflation or changes in inflation expectations.

rr_RiskReturnAbstract

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | Issuer Risk [Member]

rr_RiskTextBlock

◼

Interest Rate Risk— Interest rate risk refers to the risk of fluctuations in the value of a fixed-income security due to changes in the general level of interest rates. Interest rate changes can be sudden and unpredictable and are influenced by a number of factors, including government policy, monetary policy, inflation expectations, perceptions of risk, and supply and demand for fixed-income securities. An increase in interest rates generally will cause the value of fixed-income securities to decline. Securities with longer maturities generally are more sensitive to interest rate changes and subject to greater fluctuations in value. Changes in interest rates may have unpredictable effects on fixed-income markets and result in heightened volatility and lower liquidity for certain instruments, which may

adversely affect the Fund’s performance. During periods of very low or negative interest rates, the Fund may be unable to maintain positive returns or pay dividends to shareholders.

rr_RiskReturnAbstract

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | Management Risk [Member]

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.

rr_RiskReturnAbstract

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | Market Risk and Selection Risk [Member]

rr_RiskTextBlock

◼

Management Risk — As the Fund may not fully replicate the Underlying Index, it is subject to the risk that BlackRock’s investment strategy may not produce the intended results.

rr_RiskReturnAbstract

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | Risk of Investing in the United States [Member]

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.

rr_RiskReturnAbstract

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | Investor A Shares

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.

Distribution and/or Service (12b-1) Fees

rr_RiskReturnAbstract

Management Fee

rr_ManagementFeesOverAssets

0.01%

^[1]

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.25%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.51%

Fee Waivers and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.15%)

^[1],[2]

Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements

rr_NetExpensesOverAssets

0.36%

^[1],[2]

rr_ExpenseExampleYear01

$ 37

3 Years

rr_ExpenseExampleYear03

148

Highest Quarterly Return, Label

rr_ExpenseExampleYear05

270

10 Years

rr_ExpenseExampleYear10

$ 626

2017

rr_AnnualReturn2017

0.77%

2018

rr_AnnualReturn2018

0.22%

2019

rr_AnnualReturn2019

4.39%

2020

rr_AnnualReturn2020

4.64%

2021

rr_AnnualReturn2021

4.89%

2022

rr_AnnualReturn2022

(3.15%)

2023

rr_AnnualReturn2023

4.22%

2024

rr_AnnualReturn2024

4.45%

rr_HighestQuarterlyReturnLabel

highest return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2024

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

2.50%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2022

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(2.76%)

rr_AverageAnnualReturnYear01

4.45%

rr_AverageAnnualReturnYear05

2.96%

rr_AverageAnnualReturnSinceInception

2.51%

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | Institutional Shares

rr_AverageAnnualReturnInceptionDate

Feb. 16, 2016

Distribution and/or Service (12b-1) Fees

rr_RiskReturnAbstract

Management Fee

rr_ManagementFeesOverAssets

0.01%

^[1]

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.12%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.13%

Fee Waivers and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.02%)

^[1],[2]

Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements

rr_NetExpensesOverAssets

0.11%

^[1],[2]

rr_ExpenseExampleYear01

$ 11

3 Years

rr_ExpenseExampleYear03

rr_ExpenseExampleYear05

10 Years

rr_ExpenseExampleYear10

$ 164

rr_AverageAnnualReturnYear01

4.72%

rr_AverageAnnualReturnYear05

3.23%

rr_AverageAnnualReturnSinceInception

2.78%

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | Return After Taxes on Distributions | Investor A Shares

rr_AverageAnnualReturnInceptionDate

Feb. 16, 2016

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

2.75%

rr_AverageAnnualReturnYear05

1.44%

rr_AverageAnnualReturnSinceInception

1.29%

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | Return After Taxes on Distributions and Sale of Fund Shares | Investor A Shares

rr_AverageAnnualReturnInceptionDate

Feb. 16, 2016

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

2.62%

rr_AverageAnnualReturnYear05

1.62%

rr_AverageAnnualReturnSinceInception

1.39%

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | ICE BofA U.S. Broad Market Index (Reflects no deduction for fees, expenses or taxes)

rr_AverageAnnualReturnInceptionDate

Feb. 16, 2016

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

1.47%

^[3]

rr_AverageAnnualReturnYear05

(0.34%)

^[3]

Investor A, Institutional | iShares Short-Term TIPS Bond Index Fund | Bloomberg U.S. Treasury Inflation-Protected Securities (TIPS) 0-5 Years Index (Series-L) (Reflects no deduction for fees, expenses or taxes)

rr_AverageAnnualReturnSinceInception

1.26%

^[3]

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

4.69%

rr_AverageAnnualReturnYear05

3.34%