XML 11 R2.htm IDEA: XBRL DOCUMENT v3.25.1
Shareholder Report
 6 Months Ended
Jan. 31, 2025
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, 2025
C000155940 [Member]  
Shareholder Report [Line Items]  
Fund Name iShares Russell Mid-Cap Index Fund
Class Name Institutional Shares
Trading Symbol BRMIX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about iShares Russell Mid-Cap Index Fund (the “Fund”) for the period of August 1, 2024 to January 31, 2025.
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.
Additional Information Phone Number (800) 441‑7762
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)
Class name Costs of a $10,000
investment		 Costs paid as a percentage of a
$10,000 investment
Institutional Shares $5 0.10%(a)
​(a)
Annualized.
Expenses Paid, Amount $ 5
Expense Ratio, Percent 0.10% [1]
Performance Past Does Not Indicate Future [Text] Past performance is not an indication of future results.
Average Annual Return [Table Text Block]
Average annual total returns
6-Month
Total
Returns		 1 Year 5 Years Since Fund
Inception
Institutional Shares 9.33 % 21.89 % 10.98 % 9.94 %
Russell 3000® Index 10.42 26.32 14.60 12.95
Russell Midcap® Index 9.41 21.99 11.02 9.98
Performance Inception Date May 13, 2015
No Deduction of Taxes [Text Block] Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares.
Updated Performance Information Location [Text Block] Visit blackrock.com for more recent performance information.
Net Assets $ 2,109,449,555
Holdings Count | Holding 813
Investment Company Portfolio Turnover 5.00%
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $2,109,449,555
Number of Portfolio Holdings 813
Portfolio Turnover Rate 5%
Holdings [Text Block]
What did the Fund invest in?
(as of January 31, 2025)
Sector allocation
Sector(a) Percent of
Net Assets
Industrials 16.9 %
Financials 16.9 %
Information Technology 14.0 %
Consumer Discretionary 10.5 %
Health Care 9.5 %
Real Estate 7.3 %
Utilities 5.4 %
Materials 5.3 %
Energy 5.2 %
Consumer Staples 4.5 %
Other* 4.3 %
Short-Term Securities 2.7 %
Liabilities in Excess of Other Assets (2.5 )
Ten largest holdings
Security(b) Percent of
Net Assets
Palantir Technologies, Inc., Class A 1.3 %
AppLovin Corp., Class A 0.8 %
iShares Russell Mid-Cap ETF 0.7 %
Arthur J Gallagher & Co. 0.6 %
Williams Cos., Inc. 0.5 %
Bank of New York Mellon Corp. 0.5 %
Royal Caribbean Cruises Ltd. 0.5 %
Hilton Worldwide Holdings, Inc. 0.5 %
Aflac, Inc. 0.5 %
Coinbase Global, Inc., Class A 0.5 %
​(a)
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund for compliance purposes.
​(b)
Excludes short-term securities.
​*
Ten largest sectors are presented. Additional sectors are found in Other.
Largest Holdings [Text Block]
Ten largest holdings
Security(b) Percent of
Net Assets
Palantir Technologies, Inc., Class A 1.3 %
AppLovin Corp., Class A 0.8 %
iShares Russell Mid-Cap ETF 0.7 %
Arthur J Gallagher & Co. 0.6 %
Williams Cos., Inc. 0.5 %
Bank of New York Mellon Corp. 0.5 %
Royal Caribbean Cruises Ltd. 0.5 %
Hilton Worldwide Holdings, Inc. 0.5 %
Aflac, Inc. 0.5 %
Coinbase Global, Inc., Class A 0.5 %
(b)Excludes short-term securities.
C000163604 [Member]  
Shareholder Report [Line Items]  
Fund Name iShares Russell Mid-Cap Index Fund
Class Name Investor A Shares
Trading Symbol BRMAX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about iShares Russell Mid-Cap Index Fund (the “Fund”) for the period of August 1, 2024 to January 31, 2025.
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.
Additional Information Phone Number (800) 441‑7762
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)
Class name Costs of a $10,000
investment		 Costs paid as a percentage of a
$10,000 investment
Investor A Shares $19 0.36%(a)
​(a)
Annualized.
Expenses Paid, Amount $ 19
Expense Ratio, Percent 0.36% [2]
Performance Past Does Not Indicate Future [Text] Past performance is not an indication of future results.
Average Annual Return [Table Text Block]
Average annual total returns
6-Month
Total
Returns		 1 Year 5 Years Since Fund
Inception
Investor A Shares 9.24 % 21.61 % 10.69 % 9.67 %
Russell 3000® Index 10.42 26.32 14.60 12.95
Russell Midcap® Index 9.41 21.99 11.02 9.98
Performance Inception Date May 13, 2015
No Deduction of Taxes [Text Block] Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares.
Updated Performance Information Location [Text Block] Visit blackrock.com for more recent performance information.
Net Assets $ 2,109,449,555
Holdings Count | Holding 813
Investment Company Portfolio Turnover 5.00%
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $2,109,449,555
Number of Portfolio Holdings 813
Portfolio Turnover Rate 5%
Holdings [Text Block]
What did the Fund invest in?
(as of January 31, 2025)
Sector allocation
Sector(a) Percent of
Net Assets
Industrials 16.9 %
Financials 16.9 %
Information Technology 14.0 %
Consumer Discretionary 10.5 %
Health Care 9.5 %
Real Estate 7.3 %
Utilities 5.4 %
Materials 5.3 %
Energy 5.2 %
Consumer Staples 4.5 %
Other* 4.3 %
Short-Term Securities 2.7 %
Liabilities in Excess of Other Assets (2.5 )
Ten largest holdings
Security(b) Percent of
Net Assets
Palantir Technologies, Inc., Class A 1.3 %
AppLovin Corp., Class A 0.8 %
iShares Russell Mid-Cap ETF 0.7 %
Arthur J Gallagher & Co. 0.6 %
Williams Cos., Inc. 0.5 %
Bank of New York Mellon Corp. 0.5 %
Royal Caribbean Cruises Ltd. 0.5 %
Hilton Worldwide Holdings, Inc. 0.5 %
Aflac, Inc. 0.5 %
Coinbase Global, Inc., Class A 0.5 %
​(a)
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund for compliance purposes.
​(b)
Excludes short-term securities.
​*
Ten largest sectors are presented. Additional sectors are found in Other.
Largest Holdings [Text Block]
Ten largest holdings
Security(b) Percent of
Net Assets
Palantir Technologies, Inc., Class A 1.3 %
AppLovin Corp., Class A 0.8 %
iShares Russell Mid-Cap ETF 0.7 %
Arthur J Gallagher & Co. 0.6 %
Williams Cos., Inc. 0.5 %
Bank of New York Mellon Corp. 0.5 %
Royal Caribbean Cruises Ltd. 0.5 %
Hilton Worldwide Holdings, Inc. 0.5 %
Aflac, Inc. 0.5 %
Coinbase Global, Inc., Class A 0.5 %
(b)Excludes short-term securities.
C000155941 [Member]  
Shareholder Report [Line Items]  
Fund Name iShares Russell Mid-Cap Index Fund
Class Name Class K Shares
Trading Symbol BRMKX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about iShares Russell Mid-Cap Index Fund (the “Fund”) for the period of August 1, 2024 to January 31, 2025.
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.
Additional Information Phone Number (800) 441‑7762
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)
Class name Costs of a $10,000
investment		 Costs paid as a percentage of a
$10,000 investment
Class K Shares $2 0.04%(a)
​(a)
Annualized.
Expenses Paid, Amount $ 2
Expense Ratio, Percent 0.04% [3]
Performance Past Does Not Indicate Future [Text] Past performance is not an indication of future results.
Average Annual Return [Table Text Block]
Average annual total returns
6-Month
Total
Returns		 1 Year 5 Years Since Fund
Inception
Class K Shares 9.41 % 21.98 % 11.04 % 10.00 %
Russell 3000® Index 10.42 26.32 14.60 12.95
Russell Midcap® Index 9.41 21.99 11.02 9.98
Performance Inception Date May 13, 2015
No Deduction of Taxes [Text Block] Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares.
Updated Performance Information Location [Text Block] Visit blackrock.com for more recent performance information.
Net Assets $ 2,109,449,555
Holdings Count | Holding 813
Investment Company Portfolio Turnover 5.00%
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $2,109,449,555
Number of Portfolio Holdings 813
Portfolio Turnover Rate 5%
Holdings [Text Block]
What did the Fund invest in?
(as of January 31, 2025)
Sector allocation
Sector(a) Percent of
Net Assets
Industrials 16.9 %
Financials 16.9 %
Information Technology 14.0 %
Consumer Discretionary 10.5 %
Health Care 9.5 %
Real Estate 7.3 %
Utilities 5.4 %
Materials 5.3 %
Energy 5.2 %
Consumer Staples 4.5 %
Other* 4.3 %
Short-Term Securities 2.7 %
Liabilities in Excess of Other Assets (2.5 )
Ten largest holdings
Security(b) Percent of
Net Assets
Palantir Technologies, Inc., Class A 1.3 %
AppLovin Corp., Class A 0.8 %
iShares Russell Mid-Cap ETF 0.7 %
Arthur J Gallagher & Co. 0.6 %
Williams Cos., Inc. 0.5 %
Bank of New York Mellon Corp. 0.5 %
Royal Caribbean Cruises Ltd. 0.5 %
Hilton Worldwide Holdings, Inc. 0.5 %
Aflac, Inc. 0.5 %
Coinbase Global, Inc., Class A 0.5 %
​(a)
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund for compliance purposes.
​(b)
Excludes short-term securities.
​*
Ten largest sectors are presented. Additional sectors are found in Other.
Largest Holdings [Text Block]
Ten largest holdings
Security(b) Percent of
Net Assets
Palantir Technologies, Inc., Class A 1.3 %
AppLovin Corp., Class A 0.8 %
iShares Russell Mid-Cap ETF 0.7 %
Arthur J Gallagher & Co. 0.6 %
Williams Cos., Inc. 0.5 %
Bank of New York Mellon Corp. 0.5 %
Royal Caribbean Cruises Ltd. 0.5 %
Hilton Worldwide Holdings, Inc. 0.5 %
Aflac, Inc. 0.5 %
Coinbase Global, Inc., Class A 0.5 %
(b)Excludes short-term securities.
C000159049 [Member]  
Shareholder Report [Line Items]  
Fund Name iShares Total U.S. Stock Market Index Fund
Class Name Institutional Shares
Trading Symbol BITSX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about iShares Total U.S. Stock Market Index Fund (the “Fund”) for the period of August 1, 2024 to January 31, 2025.
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.
Additional Information Phone Number (800) 441‑7762
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)
Class name Costs of a $10,000
investment		 Costs paid as a percentage of a
$10,000 investment
Institutional Shares $3 0.06%(a)
​(a)
Annualized.
Expenses Paid, Amount $ 3
Expense Ratio, Percent 0.06% [4]
Performance Past Does Not Indicate Future [Text] Past performance is not an indication of future results.
Average Annual Return [Table Text Block]
Average annual total returns
6-Month
Total
Returns		 1 Year 5 Years Since Fund
Inception
Institutional Shares 10.40 % 26.34 % 14.58 % 13.34 %
Russell 3000® Index 10.42 26.32 14.60 13.37
Performance Inception Date Aug. 13, 2015
No Deduction of Taxes [Text Block] Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares.
Updated Performance Information Location [Text Block] Visit blackrock.com for more recent performance information.
Net Assets $ 3,930,486,575
Holdings Count | Holding 2,738
Investment Company Portfolio Turnover 3.00%
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $3,930,486,575
Number of Portfolio Holdings 2,738
Portfolio Turnover Rate 3%
Holdings [Text Block]
What did the Fund invest in?
(as of January 31, 2025)
Sector allocation
Sector(a) Percent of
Net Assets
Information Technology 28.2 %
Financials 14.6 %
Consumer Discretionary 11.4 %
Health Care 10.6 %
Industrials 9.5 %
Communication Services 9.4 %
Consumer Staples 5.2 %
Energy 3.3 %
Real Estate 2.5 %
Materials 2.3 %
Other* 2.8 %
Short-Term Securities 1.2 %
Liabilities in Excess of Other Assets (1.0 )
Ten largest holdings
Security(b) Percent of
Net Assets
Apple, Inc. 5.7 %
Microsoft Corp. 5.3 %
NVIDIA Corp. 4.8 %
Amazon.com, Inc. 3.8 %
Meta Platforms, Inc., Class A 2.6 %
Alphabet, Inc., Class A 2.0 %
Tesla, Inc. 1.9 %
Broadcom, Inc. 1.7 %
Alphabet, Inc., Class C 1.7 %
Berkshire Hathaway, Inc., Class B 1.5 %
​(a)
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund for compliance purposes.
​(b)
Excludes short-term securities.
​*
Ten largest sectors are presented. Additional sectors are found in Other.
Largest Holdings [Text Block]
Ten largest holdings
Security(b) Percent of
Net Assets
Apple, Inc. 5.7 %
Microsoft Corp. 5.3 %
NVIDIA Corp. 4.8 %
Amazon.com, Inc. 3.8 %
Meta Platforms, Inc., Class A 2.6 %
Alphabet, Inc., Class A 2.0 %
Tesla, Inc. 1.9 %
Broadcom, Inc. 1.7 %
Alphabet, Inc., Class C 1.7 %
Berkshire Hathaway, Inc., Class B 1.5 %
(b)Excludes short-term securities.
C000159048 [Member]  
Shareholder Report [Line Items]  
Fund Name iShares Total U.S. Stock Market Index Fund
Class Name Investor A Shares
Trading Symbol BASMX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about iShares Total U.S. Stock Market Index Fund (the “Fund”) for the period of August 1, 2024 to January 31, 2025.
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.
Additional Information Phone Number (800) 441‑7762
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)
Class name Costs of a $10,000
investment		 Costs paid as a percentage of a
$10,000 investment
Investor A Shares $17 0.33%(a)
​(a)
Annualized.
Expenses Paid, Amount $ 17
Expense Ratio, Percent 0.33% [5]
Performance Past Does Not Indicate Future [Text] Past performance is not an indication of future results.
Average Annual Return [Table Text Block]
Average annual total returns
6-Month
Total
Returns		 1 Year 5 Years Since Fund
Inception
Investor A Shares 10.24 % 25.96 % 14.30 % 13.06 %
Russell 3000® Index 10.42 26.32 14.60 13.37
Performance Inception Date Aug. 13, 2015
No Deduction of Taxes [Text Block] Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares.
Updated Performance Information Location [Text Block] Visit blackrock.com for more recent performance information.
Net Assets $ 3,930,486,575
Holdings Count | Holding 2,738
Investment Company Portfolio Turnover 3.00%
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $3,930,486,575
Number of Portfolio Holdings 2,738
Portfolio Turnover Rate 3%
Holdings [Text Block]
What did the Fund invest in?
(as of January 31, 2025)
Sector allocation
Sector(a) Percent of
Net Assets
Information Technology 28.2 %
Financials 14.6 %
Consumer Discretionary 11.4 %
Health Care 10.6 %
Industrials 9.5 %
Communication Services 9.4 %
Consumer Staples 5.2 %
Energy 3.3 %
Real Estate 2.5 %
Materials 2.3 %
Other* 2.8 %
Short-Term Securities 1.2 %
Liabilities in Excess of Other Assets (1.0 )
Ten largest holdings
Security(b) Percent of
Net Assets
Apple, Inc. 5.7 %
Microsoft Corp. 5.3 %
NVIDIA Corp. 4.8 %
Amazon.com, Inc. 3.8 %
Meta Platforms, Inc., Class A 2.6 %
Alphabet, Inc., Class A 2.0 %
Tesla, Inc. 1.9 %
Broadcom, Inc. 1.7 %
Alphabet, Inc., Class C 1.7 %
Berkshire Hathaway, Inc., Class B 1.5 %
​(a)
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund for compliance purposes.
​(b)
Excludes short-term securities.
​*
Ten largest sectors are presented. Additional sectors are found in Other.
Largest Holdings [Text Block]
Ten largest holdings
Security(b) Percent of
Net Assets
Apple, Inc. 5.7 %
Microsoft Corp. 5.3 %
NVIDIA Corp. 4.8 %
Amazon.com, Inc. 3.8 %
Meta Platforms, Inc., Class A 2.6 %
Alphabet, Inc., Class A 2.0 %
Tesla, Inc. 1.9 %
Broadcom, Inc. 1.7 %
Alphabet, Inc., Class C 1.7 %
Berkshire Hathaway, Inc., Class B 1.5 %
(b)Excludes short-term securities.
C000159050 [Member]  
Shareholder Report [Line Items]  
Fund Name iShares Total U.S. Stock Market Index Fund
Class Name Class K Shares
Trading Symbol BKTSX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about iShares Total U.S. Stock Market Index Fund (the “Fund”) for the period of August 1, 2024 to January 31, 2025.
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.
Additional Information Phone Number (800) 441‑7762
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)
Class name Costs of a $10,000
investment		 Costs paid as a percentage of a
$10,000 investment
Class K Shares $1 0.02%(a)
​(a)
Annualized.
Expenses Paid, Amount $ 1
Expense Ratio, Percent 0.02% [6]
Performance Past Does Not Indicate Future [Text] Past performance is not an indication of future results.
Average Annual Return [Table Text Block]
Average annual total returns
6-Month
Total
Returns		 1 Year 5 Years Since Fund
Inception
Class K Shares 10.42 % 26.38 % 14.63 % 13.39 %
Russell 3000® Index 10.42 26.32 14.60 13.37
Performance Inception Date Aug. 13, 2015
No Deduction of Taxes [Text Block] Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares.
Updated Performance Information Location [Text Block] Visit blackrock.com for more recent performance information.
Net Assets $ 3,930,486,575
Holdings Count | Holding 2,738
Investment Company Portfolio Turnover 3.00%
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $3,930,486,575
Number of Portfolio Holdings 2,738
Portfolio Turnover Rate 3%
Holdings [Text Block]
What did the Fund invest in?
(as of January 31, 2025)
Sector allocation
Sector(a) Percent of
Net Assets
Information Technology 28.2 %
Financials 14.6 %
Consumer Discretionary 11.4 %
Health Care 10.6 %
Industrials 9.5 %
Communication Services 9.4 %
Consumer Staples 5.2 %
Energy 3.3 %
Real Estate 2.5 %
Materials 2.3 %
Other* 2.8 %
Short-Term Securities 1.2 %
Liabilities in Excess of Other Assets (1.0 )
Ten largest holdings
Security(b) Percent of
Net Assets
Apple, Inc. 5.7 %
Microsoft Corp. 5.3 %
NVIDIA Corp. 4.8 %
Amazon.com, Inc. 3.8 %
Meta Platforms, Inc., Class A 2.6 %
Alphabet, Inc., Class A 2.0 %
Tesla, Inc. 1.9 %
Broadcom, Inc. 1.7 %
Alphabet, Inc., Class C 1.7 %
Berkshire Hathaway, Inc., Class B 1.5 %
​(a)
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund for compliance purposes.
​(b)
Excludes short-term securities.
​*
Ten largest sectors are presented. Additional sectors are found in Other.
Largest Holdings [Text Block]
Ten largest holdings
Security(b) Percent of
Net Assets
Apple, Inc. 5.7 %
Microsoft Corp. 5.3 %
NVIDIA Corp. 4.8 %
Amazon.com, Inc. 3.8 %
Meta Platforms, Inc., Class A 2.6 %
Alphabet, Inc., Class A 2.0 %
Tesla, Inc. 1.9 %
Broadcom, Inc. 1.7 %
Alphabet, Inc., Class C 1.7 %
Berkshire Hathaway, Inc., Class B 1.5 %
(b)Excludes short-term securities.
C000159052 [Member]  
Shareholder Report [Line Items]  
Fund Name iShares Russell Small/Mid-Cap Index Fund
Class Name Institutional Shares
Trading Symbol BSMIX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about iShares Russell Small/Mid-Cap Index Fund (the “Fund”) for the period of August 1, 2024 to January 31, 2025.
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.
Additional Information Phone Number (800) 441‑7762
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)
Class name Costs of a $10,000
investment		 Costs paid as a percentage of a
$10,000 investment
Institutional Shares $6 0.11%(a)
​(a)
Annualized.
Expenses Paid, Amount $ 6
Expense Ratio, Percent 0.11% [7]
Performance Past Does Not Indicate Future [Text] Past performance is not an indication of future results.
Average Annual Return [Table Text Block]
Average annual total returns
6-Month
Total
Returns		 1 Year 5 Years Since Fund
Inception
Institutional Shares 5.40 % 19.01 % 9.94 % 9.40 %
Russell 3000® Index 10.42 26.32 14.60 13.37
Russell 2500™ Index 5.47 19.08 9.98 9.43
Performance Inception Date Aug. 13, 2015
No Deduction of Taxes [Text Block] Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares.
Updated Performance Information Location [Text Block] Visit blackrock.com for more recent performance information.
Net Assets $ 850,892,565
Holdings Count | Holding 2,446
Investment Company Portfolio Turnover 12.00%
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $850,892,565
Number of Portfolio Holdings 2,446
Portfolio Turnover Rate 12%
Holdings [Text Block]
What did the Fund invest in?
(as of January 31, 2025)
Sector allocation
Sector(a) Percent of
Net Assets
Industrials 18.7 %
Financials 17.8 %
Information Technology 12.4 %
Consumer Discretionary 12.2 %
Health Care 11.9 %
Real Estate 6.5 %
Materials 5.5 %
Energy 5.0 %
Consumer Staples 3.4 %
Communication Services 2.9 %
Other* 3.2 %
Short-Term Securities 7.3 %
Liabilities in Excess of Other Assets (6.8 )
Ten largest holdings
Security(b) Percent of
Net Assets
Robinhood Markets, Inc., Class A 0.5 %
EQT Corp. 0.5 %
Smurfit WestRock PLC 0.4 %
Carvana Co., Class A 0.4 %
iShares Russell 2000 ETF 0.4 %
Texas Pacific Land Corp. 0.4 %
Chesapeake Energy Corp. 0.4 %
NRG Energy, Inc. 0.3 %
Pure Storage, Inc., Class A 0.3 %
EMCOR Group, Inc. 0.3 %
​(a)
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund for compliance purposes.
​(b)
Excludes short-term securities.
​*
Ten largest sectors are presented. Additional sectors are found in Other.
Largest Holdings [Text Block]
Ten largest holdings
Security(b) Percent of
Net Assets
Robinhood Markets, Inc., Class A 0.5 %
EQT Corp. 0.5 %
Smurfit WestRock PLC 0.4 %
Carvana Co., Class A 0.4 %
iShares Russell 2000 ETF 0.4 %
Texas Pacific Land Corp. 0.4 %
Chesapeake Energy Corp. 0.4 %
NRG Energy, Inc. 0.3 %
Pure Storage, Inc., Class A 0.3 %
EMCOR Group, Inc. 0.3 %
(b)Excludes short-term securities.
C000159051 [Member]  
Shareholder Report [Line Items]  
Fund Name iShares Russell Small/Mid-Cap Index Fund
Class Name Investor A Shares
Trading Symbol BSMAX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about iShares Russell Small/Mid-Cap Index Fund (the “Fund”) for the period of August 1, 2024 to January 31, 2025.
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.
Additional Information Phone Number (800) 441‑7762
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)
Class name Costs of a $10,000
investment		 Costs paid as a percentage of a
$10,000 investment
Investor A Shares $19 0.37%(a)
​(a)
Annualized.
Expenses Paid, Amount $ 19
Expense Ratio, Percent 0.37% [8]
Performance Past Does Not Indicate Future [Text] Past performance is not an indication of future results.
Average Annual Return [Table Text Block]
Average annual total returns
6-Month
Total
Returns		 1 Year 5 Years Since Fund
Inception
Investor A Shares 5.28 % 18.69 % 9.67 % 9.14 %
Russell 3000® Index 10.42 26.32 14.60 13.37
Russell 2500™ Index 5.47 19.08 9.98 9.43
Performance Inception Date Aug. 13, 2015
No Deduction of Taxes [Text Block] Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares.
Updated Performance Information Location [Text Block] Visit blackrock.com for more recent performance information.
Net Assets $ 850,892,565
Holdings Count | Holding 2,446
Investment Company Portfolio Turnover 12.00%
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $850,892,565
Number of Portfolio Holdings 2,446
Portfolio Turnover Rate 12%
Holdings [Text Block]
What did the Fund invest in?
(as of January 31, 2025)
Sector allocation
Sector(a) Percent of
Net Assets
Industrials 18.7 %
Financials 17.8 %
Information Technology 12.4 %
Consumer Discretionary 12.2 %
Health Care 11.9 %
Real Estate 6.5 %
Materials 5.5 %
Energy 5.0 %
Consumer Staples 3.4 %
Communication Services 2.9 %
Other* 3.2 %
Short-Term Securities 7.3 %
Liabilities in Excess of Other Assets (6.8 )
Ten largest holdings
Security(b) Percent of
Net Assets
Robinhood Markets, Inc., Class A 0.5 %
EQT Corp. 0.5 %
Smurfit WestRock PLC 0.4 %
Carvana Co., Class A 0.4 %
iShares Russell 2000 ETF 0.4 %
Texas Pacific Land Corp. 0.4 %
Chesapeake Energy Corp. 0.4 %
NRG Energy, Inc. 0.3 %
Pure Storage, Inc., Class A 0.3 %
EMCOR Group, Inc. 0.3 %
​(a)
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund for compliance purposes.
​(b)
Excludes short-term securities.
​*
Ten largest sectors are presented. Additional sectors are found in Other.
Largest Holdings [Text Block]
Ten largest holdings
Security(b) Percent of
Net Assets
Robinhood Markets, Inc., Class A 0.5 %
EQT Corp. 0.5 %
Smurfit WestRock PLC 0.4 %
Carvana Co., Class A 0.4 %
iShares Russell 2000 ETF 0.4 %
Texas Pacific Land Corp. 0.4 %
Chesapeake Energy Corp. 0.4 %
NRG Energy, Inc. 0.3 %
Pure Storage, Inc., Class A 0.3 %
EMCOR Group, Inc. 0.3 %
(b)Excludes short-term securities.
C000159053 [Member]  
Shareholder Report [Line Items]  
Fund Name iShares Russell Small/Mid-Cap Index Fund
Class Name Class K Shares
Trading Symbol BSMKX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about iShares Russell Small/Mid-Cap Index Fund (the “Fund”) for the period of August 1, 2024 to January 31, 2025.
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.
Additional Information Phone Number (800) 441‑7762
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)
Class name Costs of a $10,000
investment		 Costs paid as a percentage of a
$10,000 investment
Class K Shares $4 0.07%(a)
​(a)
Annualized.
Expenses Paid, Amount $ 4
Expense Ratio, Percent 0.07% [9]
Performance Past Does Not Indicate Future [Text] Past performance is not an indication of future results.
Average Annual Return [Table Text Block]
Average annual total returns
6-Month
Total
Returns		 1 Year 5 Years Since Fund
Inception
Class K Shares 5.42 % 19.07 % 9.99 % 9.44 %
Russell 3000® Index 10.42 26.32 14.60 13.37
Russell 2500™ Index 5.47 19.08 9.98 9.43
Performance Inception Date Aug. 13, 2015
No Deduction of Taxes [Text Block] Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares.
Updated Performance Information Location [Text Block] Visit blackrock.com for more recent performance information.
Net Assets $ 850,892,565
Holdings Count | Holding 2,446
Investment Company Portfolio Turnover 12.00%
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $850,892,565
Number of Portfolio Holdings 2,446
Portfolio Turnover Rate 12%
Holdings [Text Block]
What did the Fund invest in?
(as of January 31, 2025)
Sector allocation
Sector(a) Percent of
Net Assets
Industrials 18.7 %
Financials 17.8 %
Information Technology 12.4 %
Consumer Discretionary 12.2 %
Health Care 11.9 %
Real Estate 6.5 %
Materials 5.5 %
Energy 5.0 %
Consumer Staples 3.4 %
Communication Services 2.9 %
Other* 3.2 %
Short-Term Securities 7.3 %
Liabilities in Excess of Other Assets (6.8 )
Ten largest holdings
Security(b) Percent of
Net Assets
Robinhood Markets, Inc., Class A 0.5 %
EQT Corp. 0.5 %
Smurfit WestRock PLC 0.4 %
Carvana Co., Class A 0.4 %
iShares Russell 2000 ETF 0.4 %
Texas Pacific Land Corp. 0.4 %
Chesapeake Energy Corp. 0.4 %
NRG Energy, Inc. 0.3 %
Pure Storage, Inc., Class A 0.3 %
EMCOR Group, Inc. 0.3 %
​(a)
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund for compliance purposes.
​(b)
Excludes short-term securities.
​*
Ten largest sectors are presented. Additional sectors are found in Other.
Largest Holdings [Text Block]
Ten largest holdings
Security(b) Percent of
Net Assets
Robinhood Markets, Inc., Class A 0.5 %
EQT Corp. 0.5 %
Smurfit WestRock PLC 0.4 %
Carvana Co., Class A 0.4 %
iShares Russell 2000 ETF 0.4 %
Texas Pacific Land Corp. 0.4 %
Chesapeake Energy Corp. 0.4 %
NRG Energy, Inc. 0.3 %
Pure Storage, Inc., Class A 0.3 %
EMCOR Group, Inc. 0.3 %
(b)Excludes short-term securities.
[1] Annualized.
[2] Annualized.
[3] Annualized.
[4] Annualized.
[5] Annualized.
[6] Annualized.
[7] Annualized.
[8] Annualized.
[9] Annualized.