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Shareholder Report
 6 Months Ended
Jan. 31, 2026
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name BlackRock Funds
Entity Central Index Key 0000844779
Entity Investment Company Type N-1A
Document Period End Date Jan. 31, 2026
C000129315  
Shareholder Report [Line Items]  
Fund Name BlackRock Short Obligations Fund
Class Name Institutional Shares
Trading Symbol BISOX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about BlackRock Short Obligations Fund (the “Fund”) for the period of August 1, 2025 to January 31, 2026.
Shareholder Report Annual or Semi-Annual Semi-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) 441-7762.
Material Fund Change Notice [Text Block]

Additional Information Website blackrock.com/fundreports
Expenses [Text Block]

What were the Fund costs for the last six months?

(based on a hypothetical $10,000 investment)

Table Summary
Class name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Institutional Shares
$15
0.29%Footnote Reference(a)
FootnoteDescription
Footnote(a)
Annualized.
Expenses Paid, Amount $ 15
Expense Ratio, Percent 0.29% [1]
AssetsNet $ 1,065,676,554
Holdings Count | Holding 250
InvestmentCompanyPortfolioTurnover 29.00%
Additional Fund Statistics [Text Block]

Key Fund statistics

Table Summary
Net Assets........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
$1,065,676,554
Number of Portfolio Holdings........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
250
Portfolio Turnover Rate........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
29%
C000198747  
Shareholder Report [Line Items]  
Fund Name BlackRock Short Obligations Fund
Class Name Investor A Shares
Trading Symbol BASOX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about BlackRock Short Obligations Fund (the “Fund”) for the period of August 1, 2025 to January 31, 2026.
Shareholder Report Annual or Semi-Annual Semi-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) 441-7762.
Material Fund Change Notice [Text Block]

Additional Information Website blackrock.com/fundreports
Expenses [Text Block]

What were the Fund costs for the last six months?

(based on a hypothetical $10,000 investment)

Table Summary
Class name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Investor A Shares
$26
0.50%Footnote Reference(a)
FootnoteDescription
Footnote(a)
Annualized.
Expenses Paid, Amount $ 26
Expense Ratio, Percent 0.50% [2]
AssetsNet $ 1,065,676,554
Holdings Count | Holding 250
InvestmentCompanyPortfolioTurnover 29.00%
Additional Fund Statistics [Text Block]

Key Fund statistics

Table Summary
Net Assets........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
$1,065,676,554
Number of Portfolio Holdings........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
250
Portfolio Turnover Rate........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
29%
C000119004  
Shareholder Report [Line Items]  
Fund Name BlackRock Short Obligations Fund
Class Name Class K Shares
Trading Symbol BBSOX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about BlackRock Short Obligations Fund (the “Fund”) for the period of August 1, 2025 to January 31, 2026.
Shareholder Report Annual or Semi-Annual Semi-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) 441-7762.
Material Fund Change Notice [Text Block]

Additional Information Website blackrock.com/fundreports
Expenses [Text Block]

What were the Fund costs for the last six months?

(based on a hypothetical $10,000 investment)

Table Summary
Class name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Class K Shares
$10
0.20%Footnote Reference(a)
FootnoteDescription
Footnote(a)
Annualized.
Expenses Paid, Amount $ 10
Expense Ratio, Percent 0.20% [3]
AssetsNet $ 1,065,676,554
Holdings Count | Holding 250
InvestmentCompanyPortfolioTurnover 29.00%
Additional Fund Statistics [Text Block]

Key Fund statistics

Table Summary
Net Assets........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
$1,065,676,554
Number of Portfolio Holdings........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
250
Portfolio Turnover Rate........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
29%
[1] Annualized.
[2] Annualized.
[3] Annualized.