XML 11 R2.htm IDEA: XBRL DOCUMENT v3.26.1
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
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, 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.
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% [1]
Net Assets $ 2,250,587,957
Holdings Count | Holding 812
Investment Company Portfolio Turnover 4.00%
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $2,250,587,957
Number of Portfolio Holdings 812
Portfolio Turnover Rate 4%
Holdings [Text Block]
What did the Fund invest in?
(as of January 31, 2026)
Sector allocation
Sector(a) Percent of
Net Assets
Industrials 18.8 %
Financials 14.6 %
Information Technology 12.3 %
Consumer Discretionary 11.2 %
Health Care 9.6 %
Real Estate 6.8 %
Utilities 5.9 %
Energy 5.9 %
Materials 5.2 %
Consumer Staples 4.7 %
Other* 4.5 %
Short-Term Securities 2.2 %
Liabilities in Excess of Other Assets (1.7 )
Ten largest holdings
Security(b) Percent of
Net Assets
iShares Russell Mid-Cap ETF 0.8 %
Western Digital Corp. 0.7 %
Bank of New York Mellon Corp. 0.6 %
Howmet Aerospace, Inc. 0.6 %
Royal Caribbean Cruises Ltd. 0.6 %
Corning, Inc. 0.6 %
Cummins, Inc. 0.6 %
Sandisk Corp. 0.6 %
Robinhood Markets, Inc., Class A 0.6 %
Vertiv Holdings Co., Class A 0.6 %
​(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
iShares Russell Mid-Cap ETF 0.8 %
Western Digital Corp. 0.7 %
Bank of New York Mellon Corp. 0.6 %
Howmet Aerospace, Inc. 0.6 %
Royal Caribbean Cruises Ltd. 0.6 %
Corning, Inc. 0.6 %
Cummins, Inc. 0.6 %
Sandisk Corp. 0.6 %
Robinhood Markets, Inc., Class A 0.6 %
Vertiv Holdings Co., Class A 0.6 %
(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, 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.
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 $18 0.35%(a)
​(a)
Annualized.
Expenses Paid, Amount $ 18
Expense Ratio, Percent 0.35% [2]
Net Assets $ 2,250,587,957
Holdings Count | Holding 812
Investment Company Portfolio Turnover 4.00%
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $2,250,587,957
Number of Portfolio Holdings 812
Portfolio Turnover Rate 4%
Holdings [Text Block]
What did the Fund invest in?
(as of January 31, 2026)
Sector allocation
Sector(a) Percent of
Net Assets
Industrials 18.8 %
Financials 14.6 %
Information Technology 12.3 %
Consumer Discretionary 11.2 %
Health Care 9.6 %
Real Estate 6.8 %
Utilities 5.9 %
Energy 5.9 %
Materials 5.2 %
Consumer Staples 4.7 %
Other* 4.5 %
Short-Term Securities 2.2 %
Liabilities in Excess of Other Assets (1.7 )
Ten largest holdings
Security(b) Percent of
Net Assets
iShares Russell Mid-Cap ETF 0.8 %
Western Digital Corp. 0.7 %
Bank of New York Mellon Corp. 0.6 %
Howmet Aerospace, Inc. 0.6 %
Royal Caribbean Cruises Ltd. 0.6 %
Corning, Inc. 0.6 %
Cummins, Inc. 0.6 %
Sandisk Corp. 0.6 %
Robinhood Markets, Inc., Class A 0.6 %
Vertiv Holdings Co., Class A 0.6 %
​(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
iShares Russell Mid-Cap ETF 0.8 %
Western Digital Corp. 0.7 %
Bank of New York Mellon Corp. 0.6 %
Howmet Aerospace, Inc. 0.6 %
Royal Caribbean Cruises Ltd. 0.6 %
Corning, Inc. 0.6 %
Cummins, Inc. 0.6 %
Sandisk Corp. 0.6 %
Robinhood Markets, Inc., Class A 0.6 %
Vertiv Holdings Co., Class A 0.6 %
(b)Excludes short-term securities.
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, 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.
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 0.09%(a)
​(a)
Annualized.
Expenses Paid, Amount $ 5
Expense Ratio, Percent 0.09% [3]
Net Assets $ 2,250,587,957
Holdings Count | Holding 812
Investment Company Portfolio Turnover 4.00%
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $2,250,587,957
Number of Portfolio Holdings 812
Portfolio Turnover Rate 4%
Holdings [Text Block]
What did the Fund invest in?
(as of January 31, 2026)
Sector allocation
Sector(a) Percent of
Net Assets
Industrials 18.8 %
Financials 14.6 %
Information Technology 12.3 %
Consumer Discretionary 11.2 %
Health Care 9.6 %
Real Estate 6.8 %
Utilities 5.9 %
Energy 5.9 %
Materials 5.2 %
Consumer Staples 4.7 %
Other* 4.5 %
Short-Term Securities 2.2 %
Liabilities in Excess of Other Assets (1.7 )
Ten largest holdings
Security(b) Percent of
Net Assets
iShares Russell Mid-Cap ETF 0.8 %
Western Digital Corp. 0.7 %
Bank of New York Mellon Corp. 0.6 %
Howmet Aerospace, Inc. 0.6 %
Royal Caribbean Cruises Ltd. 0.6 %
Corning, Inc. 0.6 %
Cummins, Inc. 0.6 %
Sandisk Corp. 0.6 %
Robinhood Markets, Inc., Class A 0.6 %
Vertiv Holdings Co., Class A 0.6 %
​(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
iShares Russell Mid-Cap ETF 0.8 %
Western Digital Corp. 0.7 %
Bank of New York Mellon Corp. 0.6 %
Howmet Aerospace, Inc. 0.6 %
Royal Caribbean Cruises Ltd. 0.6 %
Corning, Inc. 0.6 %
Cummins, Inc. 0.6 %
Sandisk Corp. 0.6 %
Robinhood Markets, Inc., Class A 0.6 %
Vertiv Holdings Co., Class A 0.6 %
(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, 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.
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]
Net Assets $ 4,308,894,559
Holdings Count | Holding 2,664
Investment Company Portfolio Turnover 3.00%
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $4,308,894,559
Number of Portfolio Holdings 2,664
Portfolio Turnover Rate 3%
Holdings [Text Block]
What did the Fund invest in?
(as of January 31, 2026)
Sector allocation
Sector(a) Percent of
Net Assets
Information Technology 30.3 %
Financials 13.1 %
Consumer Discretionary 10.3 %
Communication Services 10.2 %
Industrials 9.8 %
Health Care 9.8 %
Consumer Staples 4.7 %
Energy 3.2 %
Materials 2.3 %
Real Estate 2.2 %
Other* 3.5 %
Short-Term Securities 2.0 %
Liabilities in Excess of Other Assets (1.4 )
Ten largest holdings
Security(b) Percent of
Net Assets
NVIDIA Corp. 6.6 %
Apple, Inc. 5.6 %
Microsoft Corp. 4.7 %
Amazon.com, Inc. 3.4 %
Alphabet, Inc., Class A 2.9 %
Alphabet, Inc., Class C 2.4 %
Meta Platforms, Inc., Class A 2.3 %
Broadcom, Inc. 2.2 %
Tesla, Inc. 1.8 %
Berkshire Hathaway, Inc., Class B 1.3 %
​(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
NVIDIA Corp. 6.6 %
Apple, Inc. 5.6 %
Microsoft Corp. 4.7 %
Amazon.com, Inc. 3.4 %
Alphabet, Inc., Class A 2.9 %
Alphabet, Inc., Class C 2.4 %
Meta Platforms, Inc., Class A 2.3 %
Broadcom, Inc. 2.2 %
Tesla, Inc. 1.8 %
Berkshire Hathaway, Inc., Class B 1.3 %
(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, 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.
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]
Net Assets $ 4,308,894,559
Holdings Count | Holding 2,664
Investment Company Portfolio Turnover 3.00%
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $4,308,894,559
Number of Portfolio Holdings 2,664
Portfolio Turnover Rate 3%
Holdings [Text Block]
What did the Fund invest in?
(as of January 31, 2026)
Sector allocation
Sector(a) Percent of
Net Assets
Information Technology 30.3 %
Financials 13.1 %
Consumer Discretionary 10.3 %
Communication Services 10.2 %
Industrials 9.8 %
Health Care 9.8 %
Consumer Staples 4.7 %
Energy 3.2 %
Materials 2.3 %
Real Estate 2.2 %
Other* 3.5 %
Short-Term Securities 2.0 %
Liabilities in Excess of Other Assets (1.4 )
Ten largest holdings
Security(b) Percent of
Net Assets
NVIDIA Corp. 6.6 %
Apple, Inc. 5.6 %
Microsoft Corp. 4.7 %
Amazon.com, Inc. 3.4 %
Alphabet, Inc., Class A 2.9 %
Alphabet, Inc., Class C 2.4 %
Meta Platforms, Inc., Class A 2.3 %
Broadcom, Inc. 2.2 %
Tesla, Inc. 1.8 %
Berkshire Hathaway, Inc., Class B 1.3 %
​(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
NVIDIA Corp. 6.6 %
Apple, Inc. 5.6 %
Microsoft Corp. 4.7 %
Amazon.com, Inc. 3.4 %
Alphabet, Inc., Class A 2.9 %
Alphabet, Inc., Class C 2.4 %
Meta Platforms, Inc., Class A 2.3 %
Broadcom, Inc. 2.2 %
Tesla, Inc. 1.8 %
Berkshire Hathaway, Inc., Class B 1.3 %
(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, 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.
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]
Net Assets $ 4,308,894,559
Holdings Count | Holding 2,664
Investment Company Portfolio Turnover 3.00%
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $4,308,894,559
Number of Portfolio Holdings 2,664
Portfolio Turnover Rate 3%
Holdings [Text Block]
What did the Fund invest in?
(as of January 31, 2026)
Sector allocation
Sector(a) Percent of
Net Assets
Information Technology 30.3 %
Financials 13.1 %
Consumer Discretionary 10.3 %
Communication Services 10.2 %
Industrials 9.8 %
Health Care 9.8 %
Consumer Staples 4.7 %
Energy 3.2 %
Materials 2.3 %
Real Estate 2.2 %
Other* 3.5 %
Short-Term Securities 2.0 %
Liabilities in Excess of Other Assets (1.4 )
Ten largest holdings
Security(b) Percent of
Net Assets
NVIDIA Corp. 6.6 %
Apple, Inc. 5.6 %
Microsoft Corp. 4.7 %
Amazon.com, Inc. 3.4 %
Alphabet, Inc., Class A 2.9 %
Alphabet, Inc., Class C 2.4 %
Meta Platforms, Inc., Class A 2.3 %
Broadcom, Inc. 2.2 %
Tesla, Inc. 1.8 %
Berkshire Hathaway, Inc., Class B 1.3 %
​(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
NVIDIA Corp. 6.6 %
Apple, Inc. 5.6 %
Microsoft Corp. 4.7 %
Amazon.com, Inc. 3.4 %
Alphabet, Inc., Class A 2.9 %
Alphabet, Inc., Class C 2.4 %
Meta Platforms, Inc., Class A 2.3 %
Broadcom, Inc. 2.2 %
Tesla, Inc. 1.8 %
Berkshire Hathaway, Inc., Class B 1.3 %
(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, 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.
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% [7]
Net Assets $ 1,152,612,280
Holdings Count | Holding 2,427
Investment Company Portfolio Turnover 11.00%
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $1,152,612,280
Number of Portfolio Holdings 2,427
Portfolio Turnover Rate 11%
Holdings [Text Block]
What did the Fund invest in?
(as of January 31, 2026)
Sector allocation
Sector(a) Percent of
Net Assets
Industrials 21.4 %
Financials 16.0 %
Information Technology 14.2 %
Health Care 12.5 %
Consumer Discretionary 10.4 %
Real Estate 6.0 %
Materials 5.2 %
Energy 4.1 %
Consumer Staples 2.9 %
Utilities 2.8 %
Other* 3.8 %
Short-Term Securities 8.8 %
Liabilities in Excess of Other Assets (8.1 )
Ten largest holdings
Security(b) Percent of
Net Assets
Sandisk Corp. 1.1 %
iShares Russell 2000 ETF 0.7 %
Comfort Systems USA, Inc. 0.5 %
iShares Russell Mid-Cap ETF 0.5 %
Ciena Corp. 0.5 %
Rocket Lab Corp. 0.5 %
Coherent Corp. 0.5 %
Insmed, Inc. 0.5 %
Bloom Energy Corp., Class A 0.4 %
EMCOR Group, Inc. 0.4 %
​(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
Sandisk Corp. 1.1 %
iShares Russell 2000 ETF 0.7 %
Comfort Systems USA, Inc. 0.5 %
iShares Russell Mid-Cap ETF 0.5 %
Ciena Corp. 0.5 %
Rocket Lab Corp. 0.5 %
Coherent Corp. 0.5 %
Insmed, Inc. 0.5 %
Bloom Energy Corp., Class A 0.4 %
EMCOR Group, Inc. 0.4 %
(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, 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.
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 $20 0.37%(a)
​(a)
Annualized.
Expenses Paid, Amount $ 20
Expense Ratio, Percent 0.37% [8]
Net Assets $ 1,152,612,280
Holdings Count | Holding 2,427
Investment Company Portfolio Turnover 11.00%
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $1,152,612,280
Number of Portfolio Holdings 2,427
Portfolio Turnover Rate 11%
Holdings [Text Block]
What did the Fund invest in?
(as of January 31, 2026)
Sector allocation
Sector(a) Percent of
Net Assets
Industrials 21.4 %
Financials 16.0 %
Information Technology 14.2 %
Health Care 12.5 %
Consumer Discretionary 10.4 %
Real Estate 6.0 %
Materials 5.2 %
Energy 4.1 %
Consumer Staples 2.9 %
Utilities 2.8 %
Other* 3.8 %
Short-Term Securities 8.8 %
Liabilities in Excess of Other Assets (8.1 )
Ten largest holdings
Security(b) Percent of
Net Assets
Sandisk Corp. 1.1 %
iShares Russell 2000 ETF 0.7 %
Comfort Systems USA, Inc. 0.5 %
iShares Russell Mid-Cap ETF 0.5 %
Ciena Corp. 0.5 %
Rocket Lab Corp. 0.5 %
Coherent Corp. 0.5 %
Insmed, Inc. 0.5 %
Bloom Energy Corp., Class A 0.4 %
EMCOR Group, Inc. 0.4 %
​(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
Sandisk Corp. 1.1 %
iShares Russell 2000 ETF 0.7 %
Comfort Systems USA, Inc. 0.5 %
iShares Russell Mid-Cap ETF 0.5 %
Ciena Corp. 0.5 %
Rocket Lab Corp. 0.5 %
Coherent Corp. 0.5 %
Insmed, Inc. 0.5 %
Bloom Energy Corp., Class A 0.4 %
EMCOR Group, Inc. 0.4 %
(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, 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.
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 $7 0.12%(a)
​(a)
Annualized.
Expenses Paid, Amount $ 7
Expense Ratio, Percent 0.12% [9]
Net Assets $ 1,152,612,280
Holdings Count | Holding 2,427
Investment Company Portfolio Turnover 11.00%
Additional Fund Statistics [Text Block]
Key Fund statistics
Net Assets $1,152,612,280
Number of Portfolio Holdings 2,427
Portfolio Turnover Rate 11%
Holdings [Text Block]
What did the Fund invest in?
(as of January 31, 2026)
Sector allocation
Sector(a) Percent of
Net Assets
Industrials 21.4 %
Financials 16.0 %
Information Technology 14.2 %
Health Care 12.5 %
Consumer Discretionary 10.4 %
Real Estate 6.0 %
Materials 5.2 %
Energy 4.1 %
Consumer Staples 2.9 %
Utilities 2.8 %
Other* 3.8 %
Short-Term Securities 8.8 %
Liabilities in Excess of Other Assets (8.1 )
Ten largest holdings
Security(b) Percent of
Net Assets
Sandisk Corp. 1.1 %
iShares Russell 2000 ETF 0.7 %
Comfort Systems USA, Inc. 0.5 %
iShares Russell Mid-Cap ETF 0.5 %
Ciena Corp. 0.5 %
Rocket Lab Corp. 0.5 %
Coherent Corp. 0.5 %
Insmed, Inc. 0.5 %
Bloom Energy Corp., Class A 0.4 %
EMCOR Group, Inc. 0.4 %
​(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
Sandisk Corp. 1.1 %
iShares Russell 2000 ETF 0.7 %
Comfort Systems USA, Inc. 0.5 %
iShares Russell Mid-Cap ETF 0.5 %
Ciena Corp. 0.5 %
Rocket Lab Corp. 0.5 %
Coherent Corp. 0.5 %
Insmed, Inc. 0.5 %
Bloom Energy Corp., Class A 0.4 %
EMCOR Group, Inc. 0.4 %
(b)Excludes short-term securities.
[1]
Annualized.
[2]
Annualized.
[3]
Annualized.
[4] Annualized.
[5] Annualized.
[6] Annualized.
[7] Annualized.
[8] Annualized.
[9]
Annualized.