Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	BLACKROCK FUNDS
Prospectus Date	rr_ProspectusDate	Nov. 28, 2018
Institutional | iShares Edge MSCI USA Momentum Factor Index Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Overview <br/><br/><b>Key Facts About iShares Edge MSCI USA Momentum Factor Index Fund </b>
Objective [Heading]	rr_ObjectiveHeading	<b>Investment Objective </b>
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of iShares Edge MSCI USA Momentum Factor Index Fund (the “Fund”), a series of BlackRock FundsSM (the “Trust”), is to seek to track the investment results of an index that measures the performance of U.S. large- and mid-capitalization stocks exhibiting relatively higher momentum characteristics.
Expense [Heading]	rr_ExpenseHeading	<b>Fees and Expenses of the Fund </b>
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold Institutional Shares of the Fund.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	<b>Annual Fund Operating Expenses<br/> (expenses that you pay each year as a percentage of the value of your investment)</b>
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	November 30, 2019<br/><br/>November 30, 2028
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	<b>Portfolio Turnover: </b>
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 115% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	115.00%
Expenses Restated to Reflect Current [Text]	rr_ExpensesRestatedToReflectCurrent	Other Expenses have been restated to reflect current fees.
Expense Example [Heading]	rr_ExpenseExampleHeading	<b>Example: </b>
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	<b>Principal Investment Strategies of the Fund </b>
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund seeks to track the investment results of the MSCI USA Momentum Index (the “Underlying Index”), which has been developed by MSCI Inc. (the “Index Provider”). The Underlying Index consists of stocks exhibiting relatively higher momentum characteristics than the traditional market capitalization-weighted parent index, the MSCI USA Index (the “Parent Index”), which includes U.S. large- and mid-capitalization stocks. The Underlying Index selects and reweights securities in the Parent Index using a rules-based methodology. BFA does not have any discretion in selecting securities for the Underlying Index. The process begins with a universe of the Parent Index. A risk-adjusted price momentum, defined as the excess return over the risk-free rate divided by the annualized standard deviation of weekly returns over the past 3 years, is calculated for each security in the Parent Index over 6- and 12-month time periods. The 6- and 12-month risk-adjusted price momentum calculations are then standardized at +/-3 standard deviations and these standardized “Z-scores” (i.e., the measurement of how far above average a stock’s price momentum is versus the Parent Index) are translated into an average momentum score. Approximately 100-350 securities with the highest momentum scores are selected for inclusion in the Underlying Index. The weight of each Underlying Index constituent is determined by multiplying the security’s momentum score by its free-float market capitalization. The Underlying Index is designed to reflect the performance of an equity momentum strategy by emphasizing stocks with high price momentum, while maintaining reasonably high trading liquidity, investment capacity and moderate index turnover. As of October 31, 2018, there were 123 securities in the Underlying Index. Components primarily include information technology, consumer discretionary and financials companies. The components of the Underlying Index, and the degree to which these components represent certain industries, are likely to change over time. BFA 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 intends to align its portfolio rebalancing with the portfolio rebalancing of the Underlying Index, which is expected to be semi-annually. The Fund generally invests at least 80% of its assets, plus the amount of any borrowing for investment purposes, in securities of the Underlying Index. The Fund may invest a portion of the remainder of its assets in futures, swaps and securities not included in the Underlying Index, but which BFA believes will help the Fund track the Underlying Index.
Risk [Heading]	rr_RiskHeading	<b>Principal Risks of Investing in the Fund </b>
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Risk is inherent in all investing. The value of your investment in the Fund, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The following is a summary description of the principal risks of investing in the Fund. Asset Class Risk — Securities and other assets in the Underlying Index or in the Fund’s portfolio may underperform in comparison to the general financial markets, a particular financial market or other asset classes. Concentration Risk — The Fund reserves the right to concentrate its investments (i.e., invest 25% or more of its total assets in securities of issuers in a particular industry) to approximately the same extent that the Underlying Index concentrates in a particular industry. To the extent the Fund concentrates in a particular industry, it may be more susceptible to economic conditions and risks affecting that industry. 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, consumer preferences, social trends and marketing campaigns. 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: Volatility 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. Counterparty Risk — Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will not fulfill its contractual obligation. Market and Liquidity 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. Valuation Risk — 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. Regulatory Risk — Derivative contracts, including, without limitation, swaps, currency forwards and non-deliverable forwards, are subject to regulation under the Dodd-Frank Wall Street Reform and Consumer Protection Act (the “Dodd-Frank Act”) in the United States and under comparable regimes in Europe, Asia and other non-U.S. jurisdictions. Under the Dodd-Frank Act, certain derivatives are subject to margin requirements and swap dealers are required to collect margin from the Fund with respect to such derivatives. Specifically, regulations are now in effect that require swap dealers to post and collect variation margin (comprised of specified liquid instruments and subject to a required haircut) in connection with trading of over-the-counter (“OTC”) swaps with the Fund. Shares of investment companies (other than certain money market funds) may not be posted as collateral under these regulations. Requirements for posting of initial margin in connection with OTC swaps will be phased-in through 2020. In addition, regulations adopted by prudential regulators that will begin to take effect in 2019 will require certain bank-regulated counterparties and certain of their affiliates to include in certain financial contracts, including many derivatives contracts, terms that delay or restrict the rights of counterparties, such as the Fund, to terminate such contracts, foreclose upon collateral, exercise other default rights or restrict transfers of credit support in the event that the counterparty and/or its affiliates are subject to certain types of resolution or insolvency proceedings. The implementation of these requirements with respect to derivatives, as well as regulations under the Dodd-Frank Act regarding clearing, mandatory trading and margining of other derivatives, may increase the costs and risks to the Fund of trading in these instruments and, as a result, may affect returns to investors in the Fund. Risks Specific to Certain Derivatives Used by the Fund Futures — Futures are standardized, exchange-traded contracts that obligate a purchaser to take delivery, and a seller to make delivery, of a specific amount of an asset at a specified future date at a specified price. The primary risks associated with the use of futures contracts and options are: (a) the imperfect correlation between the change in market value of the instruments held by the Fund and the price of the futures contract or option; (b) the possible lack of a liquid secondary market for a futures contract and the resulting inability to close a futures contract when desired; (c) losses caused by unanticipated market movements, which are potentially unlimited; (d) the investment adviser’s inability to predict correctly the direction of securities prices, interest rates, currency exchange rates and other economic factors; and (e) the possibility that the counterparty will default in the performance of its obligations. Swaps — Swap agreements are two-party contracts entered into for periods ranging from a few weeks to more than one year. In a standard “swap” transaction, two parties agree to exchange the returns (or differentials in rates of return) earned or realized on particular predetermined investments or instruments, which can be adjusted for an interest factor. Swap agreements involve the risk that the party with whom the Fund has entered into the swap will default on its obligation to pay the Fund and the risk that the Fund will not be able to meet its obligations to pay the other party to the agreement. 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. Financials Sector Risk — Performance of companies in the financials sector may be adversely impacted by many factors, including, among others, changes in government regulations, economic conditions, and interest rates, credit rating downgrades, and decreased liquidity in credit markets. The impact of more stringent capital requirements and recent or future regulation of any individual financial company, or of the financials sector as a whole cannot be predicted. In recent years, cyber attacks and technology malfunctions and failures have become increasingly frequent in this sector and have caused significant losses to companies in this sector, which may negatively impact the Fund. Index Fund Risk — An index fund has operating and other expenses while an index does not. As a result, while the Fund will attempt to track the Underlying Index as closely as possible, it will tend to underperform the Underlying Index to some degree over time. If an index fund is properly correlated to its stated index, the fund will perform poorly when the index performs poorly. Index-Related Risk — There is no guarantee that the Fund’s investment results will have a high degree of correlation to those of the Underlying Index or that the Fund will achieve its investment objective. Market disruptions and regulatory restrictions could have an adverse effect on the Fund’s ability to adjust its exposure to the required levels in order to track the Underlying Index. Errors in index data, index computations or the construction of the Underlying Index in accordance with its methodology may occur from time to time and may not be identified and corrected by the Index Provider for a period of time or at all, which may have an adverse impact on the Fund and its shareholders. 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 the loss or impairment of those rights. 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. 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 any required asset segregation requirements. Increases and decreases in the value of the Fund’s portfolio will be magnified when the Fund uses leverage. Management Risk — As the Fund may not fully replicate the Underlying Index, it is subject to the risk that BFA’s investment strategy may not produce the intended results. 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. 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. 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. Momentum Securities Risk — Stocks that previously exhibited high momentum characteristics may not experience positive momentum or may experience more volatility than the market as a whole. Tracking Error Risk — The Fund may be subject to tracking error, which is the divergence of the Fund’s performance from that of the Underlying Index. Tracking error may occur because of differences between the securities and other instruments held in the Fund’s portfolio and those included in the Underlying Index, pricing differences, differences in transaction costs, the Fund’s holding of uninvested cash, differences in timing of the accrual of or the valuation of dividends or interest, tax gains or losses, changes to the Underlying Index or the costs to the Fund of complying with various new or existing regulatory requirements. This risk may be heightened during times of increased market volatility or other unusual market conditions. Tracking error also may result because the Fund incurs fees and expenses, while the Underlying Index does not.
Risk Lose Money [Text]	rr_RiskLoseMoney	You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	<b>Performance Information </b>
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 MSCI USA Momentum 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. The table includes all applicable fees. If BFA 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 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	<b>Institutional Shares </b> <br/> <b>ANNUAL TOTAL RETURNS </b> <br/> <b>iShares Edge MSCI USA Momentum Factor Index Fund </b> <br/> <b>As of 12/31</b>
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the period shown in the bar chart, the highest return for a quarter was 9.36% (quarter ended March 31, 2017) and the lowest return for a quarter was 7.78% (quarter ended June 30, 2017). The year-to-date return as of September 30, 2018 was 16.31%.
Performance Table Heading	rr_PerformanceTableHeading	<b>As of 12/31/17 <br/>Average Annual Total Returns</b>
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 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.
Institutional | iShares Edge MSCI USA Momentum Factor Index Fund | Institutional Shares
Risk/Return:	rr_RiskReturnAbstract
Management Fee	rr_ManagementFeesOverAssets	0.08%	[1]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.82%	[2],[3]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.90%	[3]
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.70%)	[1],[4]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.20%	[1],[4]
1 Year	rr_ExpenseExampleYear01	$ 20
3 Years	rr_ExpenseExampleYear03	64
5 Years	rr_ExpenseExampleYear05	113
10 Years	rr_ExpenseExampleYear10	$ 255
2017	rr_AnnualReturn2017	37.25%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	16.31%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Mar. 31, 2017
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	9.36%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2017
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	7.78%
1 Year	rr_AverageAnnualReturnYear01	37.25%
Since Inception	rr_AverageAnnualReturnSinceInception	34.40%
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 20, 2016
Institutional | iShares Edge MSCI USA Momentum Factor Index Fund | Return After Taxes on Distributions | Institutional Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	33.42%
Since Inception	rr_AverageAnnualReturnSinceInception	30.76%
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 20, 2016
Institutional | iShares Edge MSCI USA Momentum Factor Index Fund | Return After Taxes on Distributions and Sale of Fund Shares | Institutional Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	21.36%
Since Inception	rr_AverageAnnualReturnSinceInception	24.73%
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 20, 2016
Institutional | iShares Edge MSCI USA Momentum Factor Index Fund | MSCI USA Momentum Index (Reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	37.82%
Since Inception	rr_AverageAnnualReturnSinceInception	35.00%

[1] As described in the “Management of the Funds” section of the Fund’s prospectus beginning on page 46, BlackRock Fund Advisors (“BFA”) has contractually agreed to waive the management fee with respect to any portion of the Fund’s assets estimated to be attributable to investments in other equity and fixed-income mutual funds and exchange-traded funds managed by BFA or its affiliates that have a contractual management fee, through November 30, 2019. The contractual agreement 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.

[2] Other Expenses have been restated to reflect current fees.

[3] Total Annual Fund Operating Expenses do not correlate to the ratio of expenses to average net assets given in the Fund’s most recent annual report, which does not include the restatement of Other Expenses to reflect current fees.

[4] As described in the “Management of the Funds” section of the Fund’s prospectus beginning on page 46, BFA has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 0.20% of average daily net assets through November 30, 2028. The Fund may have to repay some of these waivers and/or reimbursements to BFA in the following two years. The contractual agreement 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.