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Shareholder Report
 12 Months Ended
Apr. 30, 2025
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSR
Amendment Flag false
Registrant Name BlackRock Funds
Entity Central Index Key 0000844779
Entity Investment Company Type N-1A
Document Period End Date Apr. 30, 2025
C000237396 [Member]  
Shareholder Report [Line Items]  
Fund Name Circle Reserve Fund
Class Name Institutional Shares
Trading Symbol USDXX
Annual or Semi-Annual Statement [Text Block] This annual shareholder report contains important information about Circle Reserve Fund (the “Fund”) for the period of May 1, 2024 to April 30, 2025.
Shareholder Report Annual or Semi-Annual annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441‑7450.
Additional Information Phone Number (800) 441‑7450
Additional Information Website blackrock.com/fundreports
Expenses [Text Block]
What were the Fund costs for the last year?
(based on a hypothetical $10,000 investment)
Class name Costs of a $10,000
investment		 Costs paid as a percentage of a
$10,000 investment
Institutional Shares $9 0.09%
Expenses Paid, Amount $ 9
Expense Ratio, Percent 0.09%
Performance Past Does Not Indicate Future [Text] Past performance is not an indication of future results.
Updated Performance Information Location [Text Block] Visit blackrock.com for more recent yield information.
Net Assets $ 54,214,571,561
Holdings Count | Holding 27
Advisory Fees Paid, Amount $ 19,717,756
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $54,214,571,561
Number of Portfolio Holdings 27
Net Investment Advisory Fees $19,717,756
Current seven-day yields as of April 30, 2025 (The 7-day SEC Yield may differ from the 7-Day Yield shown due to the fact that the 7-Day SEC Yield excludes distributed capital gains.)
7-Day SEC Yield 4.28%
7-Day Yield 4.28%
Holdings [Text Block]
What did the Fund invest in?
(as of April 30, 2025)
Portfolio composition
Asset Type Percent of
Net Assets
Repurchase Agreements 58.0 %
U.S. Treasury Obligations 47.0 %
Liabilities in Excess of Other Assets (5.0 )%