Label

Element

Value

Risk/Return:

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Registrant Name

dei_EntityRegistrantName

BLACKROCK FUNDS

Prospectus Date

rr_ProspectusDate

Apr. 29, 2016

Supplement [Text Block]

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BLACKROCK FUNDS^SM

BlackRock Alternative Capital Strategies Fund

(the “Fund”)

Supplement dated December 2, 2016

to the Summary Prospectus and Prospectus of the Fund, dated April 29, 2016

Effective December 1, 2016, BlackRock (as defined below) has agreed to: (i) reduce its contractual management fee rate for the Fund; and (ii) contractually cap net expenses of the Fund at lower levels for the Fund’s Investor A, Investor C and Institutional Shares. To achieve these expense caps, BlackRock has agreed to waive and/or reimburse fees or expenses if the Fund’s annual fund operating expenses, excluding certain expenses described in the prospectus, exceed a certain limit for the Fund’s Investor A, Investor C and Institutional Shares. Accordingly, effective December 1, 2016, the Fund’s Summary Prospectus and Prospectus are amended as follows:

The section of the Fund’s Summary Prospectus entitled “Key Facts About BlackRock Alternative Capital Strategies Fund—Fees and Expenses of the Fund” and the section of the Prospectus entitled “Fund Overview—Key Facts About BlackRock Alternative Capital Strategies Fund—Fees and Expenses of the Fund” are deleted in their entirety and replaced with the following:

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $25,000 in the fund complex advised by BlackRock Advisors, LLC (“BlackRock”) or its affiliates. More information about these and other discounts is available from your financial professional or your selected securities dealer, broker, investment adviser, service provider or industry professional (including BlackRock, The PNC Financial Services Group, Inc. and their respective affiliates) (each a “Financial Intermediary”) and in the “Details About the Share Classes” section on page 25 of the Fund’s prospectus and in the “Purchase of Shares” section on page II-81 of Part II of the Fund’s Statement of Additional Information.

Shareholder Fees (fees paid directly from your investment)	Investor A Shares			Investor C Shares			Institutional Shares
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)		4.00	%		None			None
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is lower)		None	1		1.00	%2		None
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)	Investor A Shares			Investor C Shares			Institutional Shares
Management Fee3,4		0.80	%		0.80	%		0.80	%
Distribution and/or Service (12b-1) Fees		0.25	%		1.00	%		None
Other Expenses4,5		0.90	%		1.04	%		0.78	%
Acquired Fund Fees and Expenses4		0.03	%		0.03	%		0.03	%
Total Annual Fund Operating Expenses4		1.98	%		2.87	%		1.61	%
Fee Waivers and/or Expense Reimbursements6		(0.75	)%		(0.89	)%		(0.63	)%
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements6		1.23	%		1.98	%		0.98	%

¹  A contingent deferred sales charge (“CDSC”) of 0.75% is assessed on certain redemptions of Investor A Shares made within 18 months after purchase where no initial sales charge was paid at time of purchase as part of an investment of $1,000,000 or more.

²  There is no CDSC on Investor C Shares after one year.

³  Management Fee has been restated to reflect current fees.

⁴  The Total Annual Fund Operating Expenses do not correlate to the ratios of expenses to average net assets given in the Fund’s most recent annual report, which do not include Acquired Fund Fees and Expenses, the restatement of Management Fee to reflect current fees or the estimation of Other Expenses to reflect current fees.

⁵  Other Expenses are based on estimated amounts for the current fiscal year.

⁶  As described in the “Management of the Fund” section of the Fund’s prospectus beginning on page 38, BlackRock 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) as a percentage of average daily net assets to 1.20% (for Investor A Shares), 1.95% (for Investor C Shares) and 0.95% (for Institutional Shares) through April 30, 2018. The Fund may have to repay some of these waivers and/or reimbursements to BlackRock in the following two years. The 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.

Example:

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:

	1 Year		3 Years		5 Years		10 Years
Investor A Shares	$	520	$	927	$	1,358	$	2,556
Investor C Shares	$	301	$	805	$	1,435	$	3,131
Institutional Shares	$	100	$	446	$	817	$	1,858

You would pay the following expenses if you did not redeem your shares:

	1 Year		3 Years		5 Years		10 Years
Investor C Shares	$	201	$	805	$	1,435	$	3,131

Portfolio Turnover:

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. For the period May 19, 2015 (commencement of operations) through December 31, 2015, the Fund’s portfolio turnover rate was 440% of the average value of its portfolio.

BlackRock Alternative Capital Strategies Fund

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

bf1_SupplementTextBlock

BLACKROCK FUNDS^SM

BlackRock Alternative Capital Strategies Fund

(the “Fund”)

Supplement dated December 2, 2016

to the Summary Prospectus and Prospectus of the Fund, dated April 29, 2016

Effective December 1, 2016, BlackRock (as defined below) has agreed to: (i) reduce its contractual management fee rate for the Fund; and (ii) contractually cap net expenses of the Fund at lower levels for the Fund’s Investor A, Investor C and Institutional Shares. To achieve these expense caps, BlackRock has agreed to waive and/or reimburse fees or expenses if the Fund’s annual fund operating expenses, excluding certain expenses described in the prospectus, exceed a certain limit for the Fund’s Investor A, Investor C and Institutional Shares. Accordingly, effective December 1, 2016, the Fund’s Summary Prospectus and Prospectus are amended as follows:

The section of the Fund’s Summary Prospectus entitled “Key Facts About BlackRock Alternative Capital Strategies Fund—Fees and Expenses of the Fund” and the section of the Prospectus entitled “Fund Overview—Key Facts About BlackRock Alternative Capital Strategies Fund—Fees and Expenses of the Fund” are deleted in their entirety and replaced with the following:

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $25,000 in the fund complex advised by BlackRock Advisors, LLC (“BlackRock”) or its affiliates. More information about these and other discounts is available from your financial professional or your selected securities dealer, broker, investment adviser, service provider or industry professional (including BlackRock, The PNC Financial Services Group, Inc. and their respective affiliates) (each a “Financial Intermediary”) and in the “Details About the Share Classes” section on page 25 of the Fund’s prospectus and in the “Purchase of Shares” section on page II-81 of Part II of the Fund’s Statement of Additional Information.

Shareholder Fees (fees paid directly from your investment)	Investor A Shares			Investor C Shares			Institutional Shares
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)		4.00	%		None			None
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is lower)		None	1		1.00	%2		None
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)	Investor A Shares			Investor C Shares			Institutional Shares
Management Fee3,4		0.80	%		0.80	%		0.80	%
Distribution and/or Service (12b-1) Fees		0.25	%		1.00	%		None
Other Expenses4,5		0.90	%		1.04	%		0.78	%
Acquired Fund Fees and Expenses4		0.03	%		0.03	%		0.03	%
Total Annual Fund Operating Expenses4		1.98	%		2.87	%		1.61	%
Fee Waivers and/or Expense Reimbursements6		(0.75	)%		(0.89	)%		(0.63	)%
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements6		1.23	%		1.98	%		0.98	%

¹  A contingent deferred sales charge (“CDSC”) of 0.75% is assessed on certain redemptions of Investor A Shares made within 18 months after purchase where no initial sales charge was paid at time of purchase as part of an investment of $1,000,000 or more.

²  There is no CDSC on Investor C Shares after one year.

³  Management Fee has been restated to reflect current fees.

⁴  The Total Annual Fund Operating Expenses do not correlate to the ratios of expenses to average net assets given in the Fund’s most recent annual report, which do not include Acquired Fund Fees and Expenses, the restatement of Management Fee to reflect current fees or the estimation of Other Expenses to reflect current fees.

⁵  Other Expenses are based on estimated amounts for the current fiscal year.

⁶  As described in the “Management of the Fund” section of the Fund’s prospectus beginning on page 38, BlackRock 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) as a percentage of average daily net assets to 1.20% (for Investor A Shares), 1.95% (for Investor C Shares) and 0.95% (for Institutional Shares) through April 30, 2018. The Fund may have to repay some of these waivers and/or reimbursements to BlackRock in the following two years. The 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.

Example:

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:

	1 Year		3 Years		5 Years		10 Years
Investor A Shares	$	520	$	927	$	1,358	$	2,556
Investor C Shares	$	301	$	805	$	1,435	$	3,131
Institutional Shares	$	100	$	446	$	817	$	1,858

You would pay the following expenses if you did not redeem your shares:

	1 Year		3 Years		5 Years		10 Years
Investor C Shares	$	201	$	805	$	1,435	$	3,131

Portfolio Turnover:

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. For the period May 19, 2015 (commencement of operations) through December 31, 2015, the Fund’s portfolio turnover rate was 440% of the average value of its portfolio.

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 and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $25,000 in the fund complex advised by BlackRock Advisors, LLC (“BlackRock”) or its affiliates. More information about these and other discounts is available from your financial professional or your selected securities dealer, broker, investment adviser, service provider or industry professional (including BlackRock, The PNC Financial Services Group, Inc. and their respective affiliates) (each a “Financial Intermediary”) and in the “Details About the Share Classes” section on page 25 of the Fund’s prospectus and in the “Purchase of Shares” section on page II-81 of Part II of the Fund’s Statement of Additional Information.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees
(fees paid directly from your investment)

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

April 30, 2018

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. For the period May 19, 2015 (commencement of operations) through December 31, 2015, the Fund’s portfolio turnover rate was 440% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

440.00%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

A contingent deferred sales charge (“CDSC”) of 0.75% is assessed on certain redemptions of Investor A Shares made within 18 months after purchase where no initial sales charge was paid at time of purchase as part of an investment of $1,000,000 or more.

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $25,000 in the fund complex advised by BlackRock Advisors, LLC (“BlackRock”) or its affiliates.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 25,000

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other Expenses are based on estimated amounts for the current fiscal year.

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

Management Fee has been restated to reflect current fees.

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

The Total Annual Fund Operating Expenses do not correlate to the ratios of expenses to average net assets given in the Fund’s most recent annual report, which do not include Acquired Fund Fees and Expenses, the restatement of Management Fee to reflect current fees or the estimation of Other Expenses to reflect current fees.

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:

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

You would pay the following expenses if you did not redeem your shares:

BlackRock Alternative Capital Strategies Fund | Investor A Shares

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.00%

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is lower)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

^[1]

Management Fee

rr_ManagementFeesOverAssets

0.80%

^[2],[3]

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.90%

^[3],[4]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.03%

^[3]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.98%

^[3]

Fee Waivers and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.75%)

^[5]

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

rr_NetExpensesOverAssets

1.23%

^[5]

1 Year

rr_ExpenseExampleYear01

$ 520

3 Years

rr_ExpenseExampleYear03

927

5 Years

rr_ExpenseExampleYear05

1,358

10 Years

rr_ExpenseExampleYear10

$ 2,556

BlackRock Alternative Capital Strategies Fund | Investor C Shares

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is lower)

rr_MaximumDeferredSalesChargeOverOfferingPrice

1.00%

^[6]

Management Fee

rr_ManagementFeesOverAssets

0.80%

^[2],[3]

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

1.04%

^[3],[4]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.03%

^[3]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

2.87%

^[3]

Fee Waivers and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.89%)

^[5]

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

rr_NetExpensesOverAssets

1.98%

^[5]

1 Year

rr_ExpenseExampleYear01

$ 301

3 Years

rr_ExpenseExampleYear03

805

5 Years

rr_ExpenseExampleYear05

1,435

10 Years

rr_ExpenseExampleYear10

3,131

1 Year

rr_ExpenseExampleNoRedemptionYear01

201

3 Years

rr_ExpenseExampleNoRedemptionYear03

805

5 Years

rr_ExpenseExampleNoRedemptionYear05

1,435

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 3,131

BlackRock Alternative Capital Strategies Fund | Institutional Shares

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is lower)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Management Fee

rr_ManagementFeesOverAssets

0.80%

^[2],[3]

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

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.78%

^[3],[4]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.03%

^[3]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.61%

^[3]

Fee Waivers and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.63%)

^[5]

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

rr_NetExpensesOverAssets

0.98%

^[5]

1 Year

rr_ExpenseExampleYear01

$ 100

3 Years

rr_ExpenseExampleYear03

446

5 Years

rr_ExpenseExampleYear05

817

10 Years

rr_ExpenseExampleYear10

$ 1,858

[1] A contingent deferred sales charge ("CDSC") of 0.75% is assessed on certain redemptions of Investor A Shares made within 18 months after purchase where no initial sales charge was paid at time of purchase as part of an investment of $1,000,000 or more.

[2] Management Fee has been restated to reflect current fees.

[3] The Total Annual Fund Operating Expenses do not correlate to the ratios of expenses to average net assets given in the Fund's most recent annual report, which do not include Acquired Fund Fees and Expenses, the restatement of Management Fee to reflect current fees or the estimation of Other Expenses to reflect current fees.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

[5] As described in the "Management of the Fund" section of the Fund's prospectus beginning on page 38, BlackRock 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) as a percentage of average daily net assets to 1.20% (for Investor A Shares), 1.95% (for Investor C Shares) and 0.95% (for Institutional Shares) through April 30, 2018. The Fund may have to repay some of these waivers and/or reimbursements to BlackRock in the following two years. The 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.

[6] There is no CDSC on Investor C Shares after one year.