BlackRock Funds II N-CSR3 Dec 24Certified annual shareholder report (management investment company)Financial data

Company Profile

Form N-CSR Cover

Form N-CSR Cover	12 Months Ended
Form N-CSR Cover	Sep. 30, 2024
Shareholder Report [Line Items]
Document Type	N-CSR
Amendment Flag	false
Registrant Name	BlackRock Funds II
Entity Central Index Key	0001398078
Entity Investment Company Type	N-1A
Document Period End Date	Sep. 30, 2024

Shareholder Report

Shareholder Report	12 Months Ended
Shareholder Report	Sep. 30, 2024 USD ($) Holding
Shareholder Report [Line Items]
Document Type	N-CSR
Amendment Flag	false
Registrant Name	BlackRock Funds II
Entity Central Index Key	0001398078
Entity Investment Company Type	N-1A
Document Period End Date	Sep. 30, 2024
C000050684 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 80/20 Target Allocation Fund
Class Name	Institutional Shares
Trading Symbol	BIAPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 80/20 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Institutional Shares $ (a) 0.09 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 10	[1]
Expense Ratio, Percent	0.09%	[1]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Institutional Shares returned 27.65% For the same period, the MSCI All Country World Index returned 31.76% and the secondary performance benchmark, a blend of MSCI ACWI Index (56%)/MSCI USA Index (24%)/Bloomberg U.S. Universal Index (20%), returned 28.57%. What contributed to performance? Allocations to U.S. large-cap stocks, the U.S. quality factor, large-cap sustainable stocks, the U.S. large-cap growth factor, and international developed-market equities made the largest contributions. What detracted from performance? An allocation to U.S. mid-cap stocks detracted during the time it was held in the Fund. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Institutional Shares 27.65 % 11.20 % 8.86 % MSCI All Country World Index 31.76 12.19 9.39 MSCI ACWI Index (56%)/MSCI USA Index (24%)/Bloomberg U.S. Universal Index (20%) 28.57 10.83 8.88
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 1,631,685,620
Holdings Count \| Holding	20
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	97%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 20 Net Investment Advisory Fees $ Portfolio Turnover Rate 97 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Equity Funds 78.9 % Fixed-Income Funds 18.0 % Short-Term Securities 3.1 % Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 23.5 % iShares S&P 500 Growth ETF 12.6 % iShares MSCI U.S.A. Quality Factor ETF 11.1 % BlackRock U.S. Equity Factor Rotation ETF 9.6 % iShares Core Total USD Bond Market ETF 9.3 % iShares MSCI EAFE Value ETF 8.3 % iShares MSCI EAFE Growth ETF 7.4 % iShares S&P 500 Value ETF 7.4 % BlackRock Total Return Fund, Class K 6.1 % iShares MSCI Emerging Markets ex China ETF 4.7 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 23.5 % iShares S&P 500 Growth ETF 12.6 % iShares MSCI U.S.A. Quality Factor ETF 11.1 % BlackRock U.S. Equity Factor Rotation ETF 9.6 % iShares Core Total USD Bond Market ETF 9.3 % iShares MSCI EAFE Value ETF 8.3 % iShares MSCI EAFE Growth ETF 7.4 % iShares S&P 500 Value ETF 7.4 % BlackRock Total Return Fund, Class K 6.1 % iShares MSCI Emerging Markets ex China ETF 4.7 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000050685 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 80/20 Target Allocation Fund
Class Name	Investor A Shares
Trading Symbol	BAAPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 80/20 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Investor A Shares $ (a) 0.43 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 49	[2]
Expense Ratio, Percent	0.43%	[2]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Investor A Shares returned 27.34% For the same period, the MSCI All Country World Index returned 31.76% and the secondary performance benchmark, a blend of MSCI ACWI Index (56%)/MSCI USA Index (24%)/Bloomberg U.S. Universal Index (20%), returned 28.57%. What contributed to performance? Allocations to U.S. large-cap stocks, the U.S. quality factor, large-cap sustainable stocks, the U.S. large-cap growth factor, and international developed-market equities made the largest contributions. What detracted from performance? An allocation to U.S. mid-cap stocks detracted during the time it was held in the Fund. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Investor A Shares 27.34 % 10.84 % 8.49 % Investor A Shares (with sales charge) 20.66 9.65 7.91 MSCI All Country World Index 31.76 12.19 9.39 MSCI ACWI Index (56%)/MSCI USA Index (24%)/Bloomberg U.S. Universal Index (20%) 28.57 10.83 8.88
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 1,631,685,620
Holdings Count \| Holding	20
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	97%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 20 Net Investment Advisory Fees $ Portfolio Turnover Rate 97 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Equity Funds 78.9 % Fixed-Income Funds 18.0 % Short-Term Securities 3.1 % Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 23.5 % iShares S&P 500 Growth ETF 12.6 % iShares MSCI U.S.A. Quality Factor ETF 11.1 % BlackRock U.S. Equity Factor Rotation ETF 9.6 % iShares Core Total USD Bond Market ETF 9.3 % iShares MSCI EAFE Value ETF 8.3 % iShares MSCI EAFE Growth ETF 7.4 % iShares S&P 500 Value ETF 7.4 % BlackRock Total Return Fund, Class K 6.1 % iShares MSCI Emerging Markets ex China ETF 4.7 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 23.5 % iShares S&P 500 Growth ETF 12.6 % iShares MSCI U.S.A. Quality Factor ETF 11.1 % BlackRock U.S. Equity Factor Rotation ETF 9.6 % iShares Core Total USD Bond Market ETF 9.3 % iShares MSCI EAFE Value ETF 8.3 % iShares MSCI EAFE Growth ETF 7.4 % iShares S&P 500 Value ETF 7.4 % BlackRock Total Return Fund, Class K 6.1 % iShares MSCI Emerging Markets ex China ETF 4.7 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000050686 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 80/20 Target Allocation Fund
Class Name	Investor C Shares
Trading Symbol	BCAPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 80/20 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Investor C Shares $ (a) 1.18 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 134	[3]
Expense Ratio, Percent	1.18%	[3]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Investor C Shares returned 26.36% For the same period, the MSCI All Country World Index returned 31.76% and the secondary performance benchmark, a blend of MSCI ACWI Index (56%)/MSCI USA Index (24%)/Bloomberg U.S. Universal Index (20%), returned 28.57%. What contributed to performance? Allocations to U.S. large-cap stocks, the U.S. quality factor, large-cap sustainable stocks, the U.S. large-cap growth factor, and international developed-market equities made the largest contributions. What detracted from performance? An allocation to U.S. mid-cap stocks detracted during the time it was held in the Fund. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Investor C Shares 26.36 % 10.01 % 7.85 % Investor C Shares (with sales charge) 25.36 10.01 7.85 MSCI All Country World Index 31.76 12.19 9.39 MSCI ACWI Index (56%)/MSCI USA Index (24%)/Bloomberg U.S. Universal Index (20%) 28.57 10.83 8.88
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 1,631,685,620
Holdings Count \| Holding	20
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	97%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 20 Net Investment Advisory Fees $ Portfolio Turnover Rate 97 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Equity Funds 78.9 % Fixed-Income Funds 18.0 % Short-Term Securities 3.1 % Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 23.5 % iShares S&P 500 Growth ETF 12.6 % iShares MSCI U.S.A. Quality Factor ETF 11.1 % BlackRock U.S. Equity Factor Rotation ETF 9.6 % iShares Core Total USD Bond Market ETF 9.3 % iShares MSCI EAFE Value ETF 8.3 % iShares MSCI EAFE Growth ETF 7.4 % iShares S&P 500 Value ETF 7.4 % BlackRock Total Return Fund, Class K 6.1 % iShares MSCI Emerging Markets ex China ETF 4.7 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 23.5 % iShares S&P 500 Growth ETF 12.6 % iShares MSCI U.S.A. Quality Factor ETF 11.1 % BlackRock U.S. Equity Factor Rotation ETF 9.6 % iShares Core Total USD Bond Market ETF 9.3 % iShares MSCI EAFE Value ETF 8.3 % iShares MSCI EAFE Growth ETF 7.4 % iShares S&P 500 Value ETF 7.4 % BlackRock Total Return Fund, Class K 6.1 % iShares MSCI Emerging Markets ex China ETF 4.7 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000166010 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 80/20 Target Allocation Fund
Class Name	Class K Shares
Trading Symbol	BKAPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 80/20 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Class K Shares $ (a) 0.07 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 8	[4]
Expense Ratio, Percent	0.07%	[4]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Class K Shares returned 27.74% For the same period, the MSCI All Country World Index returned 31.76% and the secondary performance benchmark, a blend of MSCI ACWI Index (56%)/MSCI USA Index (24%)/Bloomberg U.S. Universal Index (20%), returned 28.57%. What contributed to performance? Allocations to U.S. large-cap stocks, the U.S. quality factor, large-cap sustainable stocks, the U.S. large-cap growth factor, and international developed-market equities made the largest contributions. What detracted from performance? An allocation to U.S. mid-cap stocks detracted during the time it was held in the Fund. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Class K Shares 27.74 % 11.23 % 8.88 % MSCI All Country World Index 31.76 12.19 9.39 MSCI ACWI Index (56%)/MSCI USA Index (24%)/Bloomberg U.S. Universal Index (20%) 28.57 10.83 8.88
Performance Inception Date	Mar. 28, 2016
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 1,631,685,620
Holdings Count \| Holding	20
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	97%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 20 Net Investment Advisory Fees $ Portfolio Turnover Rate 97 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Equity Funds 78.9 % Fixed-Income Funds 18.0 % Short-Term Securities 3.1 % Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 23.5 % iShares S&P 500 Growth ETF 12.6 % iShares MSCI U.S.A. Quality Factor ETF 11.1 % BlackRock U.S. Equity Factor Rotation ETF 9.6 % iShares Core Total USD Bond Market ETF 9.3 % iShares MSCI EAFE Value ETF 8.3 % iShares MSCI EAFE Growth ETF 7.4 % iShares S&P 500 Value ETF 7.4 % BlackRock Total Return Fund, Class K 6.1 % iShares MSCI Emerging Markets ex China ETF 4.7 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 23.5 % iShares S&P 500 Growth ETF 12.6 % iShares MSCI U.S.A. Quality Factor ETF 11.1 % BlackRock U.S. Equity Factor Rotation ETF 9.6 % iShares Core Total USD Bond Market ETF 9.3 % iShares MSCI EAFE Value ETF 8.3 % iShares MSCI EAFE Growth ETF 7.4 % iShares S&P 500 Value ETF 7.4 % BlackRock Total Return Fund, Class K 6.1 % iShares MSCI Emerging Markets ex China ETF 4.7 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000050687 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 80/20 Target Allocation Fund
Class Name	Class R Shares
Trading Symbol	BRAPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 80/20 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Class R Shares $ (a) 0.59 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 67	[5]
Expense Ratio, Percent	0.59%	[5]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Class R Shares returned 27.09% For the same period, the MSCI All Country World Index returned 31.76% and the secondary performance benchmark, a blend of MSCI ACWI Index (56%)/MSCI USA Index (24%)/Bloomberg U.S. Universal Index (20%), returned 28.57%. What contributed to performance? Allocations to U.S. large-cap stocks, the U.S. quality factor, large-cap sustainable stocks, the U.S. large-cap growth factor, and international developed-market equities made the largest contributions. What detracted from performance? An allocation to U.S. mid-cap stocks detracted during the time it was held in the Fund. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Class R Shares 27.09 % 10.66 % 8.32 % MSCI All Country World Index 31.76 12.19 9.39 MSCI ACWI Index (56%)/MSCI USA Index (24%)/Bloomberg U.S. Universal Index (20%) 28.57 10.83 8.88
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 1,631,685,620
Holdings Count \| Holding	20
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	97%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 20 Net Investment Advisory Fees $ Portfolio Turnover Rate 97 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Equity Funds 78.9 % Fixed-Income Funds 18.0 % Short-Term Securities 3.1 % Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 23.5 % iShares S&P 500 Growth ETF 12.6 % iShares MSCI U.S.A. Quality Factor ETF 11.1 % BlackRock U.S. Equity Factor Rotation ETF 9.6 % iShares Core Total USD Bond Market ETF 9.3 % iShares MSCI EAFE Value ETF 8.3 % iShares MSCI EAFE Growth ETF 7.4 % iShares S&P 500 Value ETF 7.4 % BlackRock Total Return Fund, Class K 6.1 % iShares MSCI Emerging Markets ex China ETF 4.7 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 23.5 % iShares S&P 500 Growth ETF 12.6 % iShares MSCI U.S.A. Quality Factor ETF 11.1 % BlackRock U.S. Equity Factor Rotation ETF 9.6 % iShares Core Total USD Bond Market ETF 9.3 % iShares MSCI EAFE Value ETF 8.3 % iShares MSCI EAFE Growth ETF 7.4 % iShares S&P 500 Value ETF 7.4 % BlackRock Total Return Fund, Class K 6.1 % iShares MSCI Emerging Markets ex China ETF 4.7 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000050742 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 40/60 Target Allocation Fund
Class Name	Institutional Shares
Trading Symbol	BIMPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 40/60 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Institutional Shares $ (a) 0.10 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 11	[6]
Expense Ratio, Percent	0.10%	[6]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Institutional Shares returned 19.88% For the same period, the Bloomberg U.S. Universal Index returned 12.08% and the secondary performance benchmark, a blend of MSCI ACWI Index (28%)/MSCI USA Index (12%)/Bloomberg U.S. Universal Index (60%), returned 20.14%. What contributed to performance? Allocations to U.S. large-cap stocks, the U.S. quality factor, large-cap sustainable stocks, core U.S. fixed income, and a total return bond strategy made the largest contributions. What detracted from performance? Allocations to U.S. mid-cap stocks, a systematic high yield bond strategy, and the U.S. minimum volatility factor detracted in the time they were held in the Fund. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Institutional Shares 19.88 % 6.33 % 5.87 % Bloomberg U.S. Universal Index 12.08 0.70 2.15 MSCI ACWI Index (28%)/MSCI USA Index (12%)/Bloomberg U.S. Universal Index (60%) 20.14 5.91 5.64 MSCI All Country World Index 31.76 12.19 9.39
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 657,031,880
Holdings Count \| Holding	21
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	103%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 21 Net Investment Advisory Fees $ Portfolio Turnover Rate 103 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Fixed-Income Funds 55.6 % Equity Funds 39.9 % Short-Term Securities 4.5 % Ten largest holdings Security Percent of Total (a) BlackRock Total Return Fund, Class K 18.2 % iShares Core Total USD Bond Market ETF 15.6 % iShares Core S&P 500 ETF 13.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 10.4 % BlackRock U.S. Mortgage Portfolio, Institutional Class 7.8 % BlackRock Flexible Income ETF 7.6 % iShares S&P 500 Growth ETF 7.0 % iShares MSCI U.S.A. Quality Factor ETF 6.8 % iShares 20+ Year Treasury Bond ETF 6.5 % BlackRock U.S. Equity Factor Rotation ETF 6.5 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) BlackRock Total Return Fund, Class K 18.2 % iShares Core Total USD Bond Market ETF 15.6 % iShares Core S&P 500 ETF 13.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 10.4 % BlackRock U.S. Mortgage Portfolio, Institutional Class 7.8 % BlackRock Flexible Income ETF 7.6 % iShares S&P 500 Growth ETF 7.0 % iShares MSCI U.S.A. Quality Factor ETF 6.8 % iShares 20+ Year Treasury Bond ETF 6.5 % BlackRock U.S. Equity Factor Rotation ETF 6.5 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000050743 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 40/60 Target Allocation Fund
Class Name	Investor A Shares
Trading Symbol	BAMPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 40/60 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Investor A Shares $ (a) 0.44 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 48	[7]
Expense Ratio, Percent	0.44%	[7]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Investor A Shares returned 19.47% For the same period, the Bloomberg U.S. Universal Index returned 12.08% and the secondary performance benchmark, a blend of MSCI ACWI Index (28%)/MSCI USA Index (12%)/Bloomberg U.S. Universal Index (60%), returned 20.14%. What contributed to performance? Allocations to U.S. large-cap stocks, the U.S. quality factor, large-cap sustainable stocks, core U.S. fixed income, and a total return bond strategy made the largest contributions. What detracted from performance? Allocations to U.S. mid-cap stocks, a systematic high yield bond strategy, and the U.S. minimum volatility factor detracted in the time they were held in the Fund. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Investor A Shares 19.47 % 5.98 % 5.51 % Investor A Shares (with sales charge) 13.20 4.84 4.95 Bloomberg U.S. Universal Index 12.08 0.70 2.15 MSCI ACWI Index (28%)/MSCI USA Index (12%)/Bloomberg U.S. Universal Index (60%) 20.14 5.91 5.64 MSCI All Country World Index 31.76 12.19 9.39
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 657,031,880
Holdings Count \| Holding	21
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	103%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 21 Net Investment Advisory Fees $ Portfolio Turnover Rate 103 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Fixed-Income Funds 55.6 % Equity Funds 39.9 % Short-Term Securities 4.5 % Ten largest holdings Security Percent of Total (a) BlackRock Total Return Fund, Class K 18.2 % iShares Core Total USD Bond Market ETF 15.6 % iShares Core S&P 500 ETF 13.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 10.4 % BlackRock U.S. Mortgage Portfolio, Institutional Class 7.8 % BlackRock Flexible Income ETF 7.6 % iShares S&P 500 Growth ETF 7.0 % iShares MSCI U.S.A. Quality Factor ETF 6.8 % iShares 20+ Year Treasury Bond ETF 6.5 % BlackRock U.S. Equity Factor Rotation ETF 6.5 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) BlackRock Total Return Fund, Class K 18.2 % iShares Core Total USD Bond Market ETF 15.6 % iShares Core S&P 500 ETF 13.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 10.4 % BlackRock U.S. Mortgage Portfolio, Institutional Class 7.8 % BlackRock Flexible Income ETF 7.6 % iShares S&P 500 Growth ETF 7.0 % iShares MSCI U.S.A. Quality Factor ETF 6.8 % iShares 20+ Year Treasury Bond ETF 6.5 % BlackRock U.S. Equity Factor Rotation ETF 6.5 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000050744 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 40/60 Target Allocation Fund
Class Name	Investor C Shares
Trading Symbol	BCMPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 40/60 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Investor C Shares $ (a) 1.19 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 130	[8]
Expense Ratio, Percent	1.19%	[8]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Investor C Shares returned 18.58% For the same period, the Bloomberg U.S. Universal Index returned 12.08% and the secondary performance benchmark, a blend of MSCI ACWI Index (28%)/MSCI USA Index (12%)/Bloomberg U.S. Universal Index (60%), returned 20.14%. What contributed to performance? Allocations to U.S. large-cap stocks, the U.S. quality factor, large-cap sustainable stocks, core U.S. fixed income, and a total return bond strategy made the largest contributions. What detracted from performance? Allocations to U.S. mid-cap stocks, a systematic high yield bond strategy, and the U.S. minimum volatility factor detracted in the time they were held in the Fund. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Investor C Shares 18.58 % 5.18 % 4.89 % Investor C Shares (with sales charge) 17.58 5.18 4.89 Bloomberg U.S. Universal Index 12.08 0.70 2.15 MSCI ACWI Index (28%)/MSCI USA Index (12%)/Bloomberg U.S. Universal Index (60%) 20.14 5.91 5.64 MSCI All Country World Index 31.76 12.19 9.39
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 657,031,880
Holdings Count \| Holding	21
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	103%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 21 Net Investment Advisory Fees $ Portfolio Turnover Rate 103 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Fixed-Income Funds 55.6 % Equity Funds 39.9 % Short-Term Securities 4.5 % Ten largest holdings Security Percent of Total (a) BlackRock Total Return Fund, Class K 18.2 % iShares Core Total USD Bond Market ETF 15.6 % iShares Core S&P 500 ETF 13.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 10.4 % BlackRock U.S. Mortgage Portfolio, Institutional Class 7.8 % BlackRock Flexible Income ETF 7.6 % iShares S&P 500 Growth ETF 7.0 % iShares MSCI U.S.A. Quality Factor ETF 6.8 % iShares 20+ Year Treasury Bond ETF 6.5 % BlackRock U.S. Equity Factor Rotation ETF 6.5 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) BlackRock Total Return Fund, Class K 18.2 % iShares Core Total USD Bond Market ETF 15.6 % iShares Core S&P 500 ETF 13.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 10.4 % BlackRock U.S. Mortgage Portfolio, Institutional Class 7.8 % BlackRock Flexible Income ETF 7.6 % iShares S&P 500 Growth ETF 7.0 % iShares MSCI U.S.A. Quality Factor ETF 6.8 % iShares 20+ Year Treasury Bond ETF 6.5 % BlackRock U.S. Equity Factor Rotation ETF 6.5 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000166011 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 40/60 Target Allocation Fund
Class Name	Class K Shares
Trading Symbol	BKMPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 40/60 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Class K Shares $ (a) 0.08 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 9	[9]
Expense Ratio, Percent	0.08%	[9]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Class K Shares returned 19.88% For the same period, the Bloomberg U.S. Universal Index returned 12.08% and the secondary performance benchmark, a blend of MSCI ACWI Index (28%)/MSCI USA Index (12%)/Bloomberg U.S. Universal Index (60%), returned 20.14%. What contributed to performance? Allocations to U.S. large-cap stocks, the U.S. quality factor, large-cap sustainable stocks, core U.S. fixed income, and a total return bond strategy made the largest contributions. What detracted from performance? Allocations to U.S. mid-cap stocks, a systematic high yield bond strategy, and the U.S. minimum volatility factor detracted in the time they were held in the Fund. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Class K Shares 19.88 % 6.34 % 5.89 % Bloomberg U.S. Universal Index 12.08 0.70 2.15 MSCI ACWI Index (28%)/MSCI USA Index (12%)/Bloomberg U.S. Universal Index (60%) 20.14 5.91 5.64 MSCI All Country World Index 31.76 12.19 9.39
Performance Inception Date	Mar. 28, 2016
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 657,031,880
Holdings Count \| Holding	21
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	103%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 21 Net Investment Advisory Fees $ Portfolio Turnover Rate 103 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Fixed-Income Funds 55.6 % Equity Funds 39.9 % Short-Term Securities 4.5 % Ten largest holdings Security Percent of Total (a) BlackRock Total Return Fund, Class K 18.2 % iShares Core Total USD Bond Market ETF 15.6 % iShares Core S&P 500 ETF 13.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 10.4 % BlackRock U.S. Mortgage Portfolio, Institutional Class 7.8 % BlackRock Flexible Income ETF 7.6 % iShares S&P 500 Growth ETF 7.0 % iShares MSCI U.S.A. Quality Factor ETF 6.8 % iShares 20+ Year Treasury Bond ETF 6.5 % BlackRock U.S. Equity Factor Rotation ETF 6.5 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) BlackRock Total Return Fund, Class K 18.2 % iShares Core Total USD Bond Market ETF 15.6 % iShares Core S&P 500 ETF 13.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 10.4 % BlackRock U.S. Mortgage Portfolio, Institutional Class 7.8 % BlackRock Flexible Income ETF 7.6 % iShares S&P 500 Growth ETF 7.0 % iShares MSCI U.S.A. Quality Factor ETF 6.8 % iShares 20+ Year Treasury Bond ETF 6.5 % BlackRock U.S. Equity Factor Rotation ETF 6.5 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000050745 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 40/60 Target Allocation Fund
Class Name	Class R Shares
Trading Symbol	BRMPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 40/60 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Class R Shares $ (a) 0.60 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 66	[10]
Expense Ratio, Percent	0.60%	[10]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Class R Shares returned 19.26% For the same period, the Bloomberg U.S. Universal Index returned 12.08% and the secondary performance benchmark, a blend of MSCI ACWI Index (28%)/MSCI USA Index (12%)/Bloomberg U.S. Universal Index (60%), returned 20.14%. What contributed to performance? Allocations to U.S. large-cap stocks, the U.S. quality factor, large-cap sustainable stocks, core U.S. fixed income, and a total return bond strategy made the largest contributions. What detracted from performance? Allocations to U.S. mid-cap stocks, a systematic high yield bond strategy, and the U.S. minimum volatility factor detracted in the time they were held in the Fund. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Class R Shares 19.26 % 5.80 % 5.34 % Bloomberg U.S. Universal Index 12.08 0.70 2.15 MSCI ACWI Index (28%)/MSCI USA Index (12%)/Bloomberg U.S. Universal Index (60%) 20.14 5.91 5.64 MSCI All Country World Index 31.76 12.19 9.39
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 657,031,880
Holdings Count \| Holding	21
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	103%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 21 Net Investment Advisory Fees $ Portfolio Turnover Rate 103 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Fixed-Income Funds 55.6 % Equity Funds 39.9 % Short-Term Securities 4.5 % Ten largest holdings Security Percent of Total (a) BlackRock Total Return Fund, Class K 18.2 % iShares Core Total USD Bond Market ETF 15.6 % iShares Core S&P 500 ETF 13.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 10.4 % BlackRock U.S. Mortgage Portfolio, Institutional Class 7.8 % BlackRock Flexible Income ETF 7.6 % iShares S&P 500 Growth ETF 7.0 % iShares MSCI U.S.A. Quality Factor ETF 6.8 % iShares 20+ Year Treasury Bond ETF 6.5 % BlackRock U.S. Equity Factor Rotation ETF 6.5 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) BlackRock Total Return Fund, Class K 18.2 % iShares Core Total USD Bond Market ETF 15.6 % iShares Core S&P 500 ETF 13.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 10.4 % BlackRock U.S. Mortgage Portfolio, Institutional Class 7.8 % BlackRock Flexible Income ETF 7.6 % iShares S&P 500 Growth ETF 7.0 % iShares MSCI U.S.A. Quality Factor ETF 6.8 % iShares 20+ Year Treasury Bond ETF 6.5 % BlackRock U.S. Equity Factor Rotation ETF 6.5 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000050785 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 20/80 Target Allocation Fund
Class Name	Institutional Shares
Trading Symbol	BICPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 20/80 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Institutional Shares $ (a) 0.10 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 11	[11]
Expense Ratio, Percent	0.10%	[11]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Institutional Shares returned 16.37% For the same period, the Bloomberg U.S. Universal Index returned 12.08% and the secondary performance benchmark, a blend of MSCI ACWI Index (14%)/MSCI USA Index (6%)/Bloomberg U.S. Universal Index (80%), returned 16.06%. What contributed to performance? Allocations to U.S. large-cap stocks, core U.S. fixed income, a bond total return strategy, and long-duration U.S. Treasuries made the largest contributions. (Duration is a measure of interest rate sensitivity.) What detracted from performance? At a time of positive returns for the financial markets more broadly, none of the Fund’s allocations detracted. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Institutional Shares 16.37 % 3.46 % 3.97 % Bloomberg U.S. Universal Index 12.08 0.70 2.15 MSCI ACWI Index (14%)/MSCI USA Index (6%)/Bloomberg U.S. Universal Index (80%) 16.06 3.34 3.93
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 440,774,854
Holdings Count \| Holding	18
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	94%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 18 Net Investment Advisory Fees $ Portfolio Turnover Rate 94 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Fixed-Income Funds 75.1 % Equity Funds 20.5 % Short-Term Securities 4.4 % Ten largest holdings Security Percent of Total (a) iShares Core Total USD Bond Market ETF 19.6 % BlackRock Total Return Fund, Class K 19.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 13.8 % BlackRock U.S. Mortgage Portfolio, Institutional Class 9.2 % BlackRock Flexible Income ETF 9.1 % iShares 20+ Year Treasury Bond ETF 8.1 % iShares Core S&P 500 ETF 6.0 % iShares Edge Investment Grade Enhanced Bond ETF 5.8 % BlackRock Cash Funds: Institutional, SL Agency Shares 5.1 % iShares S&P 500 Growth ETF 3.7 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) iShares Core Total USD Bond Market ETF 19.6 % BlackRock Total Return Fund, Class K 19.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 13.8 % BlackRock U.S. Mortgage Portfolio, Institutional Class 9.2 % BlackRock Flexible Income ETF 9.1 % iShares 20+ Year Treasury Bond ETF 8.1 % iShares Core S&P 500 ETF 6.0 % iShares Edge Investment Grade Enhanced Bond ETF 5.8 % BlackRock Cash Funds: Institutional, SL Agency Shares 5.1 % iShares S&P 500 Growth ETF 3.7 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000050786 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 20/80 Target Allocation Fund
Class Name	Investor A Shares
Trading Symbol	BACPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 20/80 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Investor A Shares $ (a) 0.44 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 48	[12]
Expense Ratio, Percent	0.44%	[12]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Investor A Shares returned 16.06% For the same period, the Bloomberg U.S. Universal Index returned 12.08% and the secondary performance benchmark, a blend of MSCI ACWI Index (14%)/MSCI USA Index (6%)/Bloomberg U.S. Universal Index (80%), returned 16.06%. What contributed to performance? Allocations to U.S. large-cap stocks, core U.S. fixed income, a bond total return strategy, and long-duration U.S. Treasuries made the largest contributions. (Duration is a measure of interest rate sensitivity.) What detracted from performance? At a time of positive returns for the financial markets more broadly, none of the Fund’s allocations detracted. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Investor A Shares 16.06 % 3.13 % 3.62 % Investor A Shares (with sales charge) 9.97 2.03 3.07 Bloomberg U.S. Universal Index 12.08 0.70 2.15 MSCI ACWI Index (14%)/MSCI USA Index (6%)/Bloomberg U.S. Universal Index (80%) 16.06 3.34 3.93
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 440,774,854
Holdings Count \| Holding	18
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	94%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 18 Net Investment Advisory Fees $ Portfolio Turnover Rate 94 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Fixed-Income Funds 75.1 % Equity Funds 20.5 % Short-Term Securities 4.4 % Ten largest holdings Security Percent of Total (a) iShares Core Total USD Bond Market ETF 19.6 % BlackRock Total Return Fund, Class K 19.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 13.8 % BlackRock U.S. Mortgage Portfolio, Institutional Class 9.2 % BlackRock Flexible Income ETF 9.1 % iShares 20+ Year Treasury Bond ETF 8.1 % iShares Core S&P 500 ETF 6.0 % iShares Edge Investment Grade Enhanced Bond ETF 5.8 % BlackRock Cash Funds: Institutional, SL Agency Shares 5.1 % iShares S&P 500 Growth ETF 3.7 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) iShares Core Total USD Bond Market ETF 19.6 % BlackRock Total Return Fund, Class K 19.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 13.8 % BlackRock U.S. Mortgage Portfolio, Institutional Class 9.2 % BlackRock Flexible Income ETF 9.1 % iShares 20+ Year Treasury Bond ETF 8.1 % iShares Core S&P 500 ETF 6.0 % iShares Edge Investment Grade Enhanced Bond ETF 5.8 % BlackRock Cash Funds: Institutional, SL Agency Shares 5.1 % iShares S&P 500 Growth ETF 3.7 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000050787 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 20/80 Target Allocation Fund
Class Name	Investor C Shares
Trading Symbol	BCCPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 20/80 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Investor C Shares $ (a) 1.19 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 128	[13]
Expense Ratio, Percent	1.19%	[13]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Investor C Shares returned 15.08% For the same period, the Bloomberg U.S. Universal Index returned 12.08% and the secondary performance benchmark, a blend of MSCI ACWI Index (14%)/MSCI USA Index (6%)/Bloomberg U.S. Universal Index (80%), returned 16.06%. What contributed to performance? Allocations to U.S. large-cap stocks, core U.S. fixed income, a bond total return strategy, and long-duration U.S. Treasuries made the largest contributions. (Duration is a measure of interest rate sensitivity.) What detracted from performance? At a time of positive returns for the financial markets more broadly, none of the Fund’s allocations detracted. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Investor C Shares 15.08 % 2.34 % 3.02 % Investor C Shares (with sales charge) 14.08 2.34 3.02 Bloomberg U.S. Universal Index 12.08 0.70 2.15 MSCI ACWI Index (14%)/MSCI USA Index (6%)/Bloomberg U.S. Universal Index (80%) 16.06 3.34 3.93
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 440,774,854
Holdings Count \| Holding	18
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	94%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 18 Net Investment Advisory Fees $ Portfolio Turnover Rate 94 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Fixed-Income Funds 75.1 % Equity Funds 20.5 % Short-Term Securities 4.4 % Ten largest holdings Security Percent of Total (a) iShares Core Total USD Bond Market ETF 19.6 % BlackRock Total Return Fund, Class K 19.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 13.8 % BlackRock U.S. Mortgage Portfolio, Institutional Class 9.2 % BlackRock Flexible Income ETF 9.1 % iShares 20+ Year Treasury Bond ETF 8.1 % iShares Core S&P 500 ETF 6.0 % iShares Edge Investment Grade Enhanced Bond ETF 5.8 % BlackRock Cash Funds: Institutional, SL Agency Shares 5.1 % iShares S&P 500 Growth ETF 3.7 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) iShares Core Total USD Bond Market ETF 19.6 % BlackRock Total Return Fund, Class K 19.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 13.8 % BlackRock U.S. Mortgage Portfolio, Institutional Class 9.2 % BlackRock Flexible Income ETF 9.1 % iShares 20+ Year Treasury Bond ETF 8.1 % iShares Core S&P 500 ETF 6.0 % iShares Edge Investment Grade Enhanced Bond ETF 5.8 % BlackRock Cash Funds: Institutional, SL Agency Shares 5.1 % iShares S&P 500 Growth ETF 3.7 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000166012 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 20/80 Target Allocation Fund
Class Name	Class K Shares
Trading Symbol	BKCPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 20/80 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Class K Shares $ (a) 0.08 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 9	[14]
Expense Ratio, Percent	0.08%	[14]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Class K Shares returned 16.39% For the same period, the Bloomberg U.S. Universal Index returned 12.08% and the secondary performance benchmark, a blend of MSCI ACWI Index (14%)/MSCI USA Index (6%)/Bloomberg U.S. Universal Index (80%), returned 16.06%. What contributed to performance? Allocations to U.S. large-cap stocks, core U.S. fixed income, a bond total return strategy, and long-duration U.S. Treasuries made the largest contributions. (Duration is a measure of interest rate sensitivity.) What detracted from performance? At a time of positive returns for the financial markets more broadly, none of the Fund’s allocations detracted. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Class K Shares 16.39 % 3.48 % 3.99 % Bloomberg U.S. Universal Index 12.08 0.70 2.15 MSCI ACWI Index (14%)/MSCI USA Index (6%)/Bloomberg U.S. Universal Index (80%) 16.06 3.34 3.93
Performance Inception Date	Mar. 28, 2016
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 440,774,854
Holdings Count \| Holding	18
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	94%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 18 Net Investment Advisory Fees $ Portfolio Turnover Rate 94 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Fixed-Income Funds 75.1 % Equity Funds 20.5 % Short-Term Securities 4.4 % Ten largest holdings Security Percent of Total (a) iShares Core Total USD Bond Market ETF 19.6 % BlackRock Total Return Fund, Class K 19.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 13.8 % BlackRock U.S. Mortgage Portfolio, Institutional Class 9.2 % BlackRock Flexible Income ETF 9.1 % iShares 20+ Year Treasury Bond ETF 8.1 % iShares Core S&P 500 ETF 6.0 % iShares Edge Investment Grade Enhanced Bond ETF 5.8 % BlackRock Cash Funds: Institutional, SL Agency Shares 5.1 % iShares S&P 500 Growth ETF 3.7 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) iShares Core Total USD Bond Market ETF 19.6 % BlackRock Total Return Fund, Class K 19.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 13.8 % BlackRock U.S. Mortgage Portfolio, Institutional Class 9.2 % BlackRock Flexible Income ETF 9.1 % iShares 20+ Year Treasury Bond ETF 8.1 % iShares Core S&P 500 ETF 6.0 % iShares Edge Investment Grade Enhanced Bond ETF 5.8 % BlackRock Cash Funds: Institutional, SL Agency Shares 5.1 % iShares S&P 500 Growth ETF 3.7 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000050788 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 20/80 Target Allocation Fund
Class Name	Class R Shares
Trading Symbol	BRCPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 20/80 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Class R Shares $ (a) 0.72 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 78	[15]
Expense Ratio, Percent	0.72%	[15]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Class R Shares returned 15.69% For the same period, the Bloomberg U.S. Universal Index returned 12.08% and the secondary performance benchmark, a blend of MSCI ACWI Index (14%)/MSCI USA Index (6%)/Bloomberg U.S. Universal Index (80%), returned 16.06%. What contributed to performance? Allocations to U.S. large-cap stocks, core U.S. fixed income, a bond total return strategy, and long-duration U.S. Treasuries made the largest contributions. (Duration is a measure of interest rate sensitivity.) What detracted from performance? At a time of positive returns for the financial markets more broadly, none of the Fund’s allocations detracted. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Class R Shares 15.69 % 2.82 % 3.32 % Bloomberg U.S. Universal Index 12.08 0.70 2.15 MSCI ACWI Index (14%)/MSCI USA Index (6%)/Bloomberg U.S. Universal Index (80%) 16.06 3.34 3.93
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 440,774,854
Holdings Count \| Holding	18
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	94%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 18 Net Investment Advisory Fees $ Portfolio Turnover Rate 94 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Fixed-Income Funds 75.1 % Equity Funds 20.5 % Short-Term Securities 4.4 % Ten largest holdings Security Percent of Total (a) iShares Core Total USD Bond Market ETF 19.6 % BlackRock Total Return Fund, Class K 19.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 13.8 % BlackRock U.S. Mortgage Portfolio, Institutional Class 9.2 % BlackRock Flexible Income ETF 9.1 % iShares 20+ Year Treasury Bond ETF 8.1 % iShares Core S&P 500 ETF 6.0 % iShares Edge Investment Grade Enhanced Bond ETF 5.8 % BlackRock Cash Funds: Institutional, SL Agency Shares 5.1 % iShares S&P 500 Growth ETF 3.7 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) iShares Core Total USD Bond Market ETF 19.6 % BlackRock Total Return Fund, Class K 19.6 % BlackRock Strategic Income Opportunities Portfolio, Class K 13.8 % BlackRock U.S. Mortgage Portfolio, Institutional Class 9.2 % BlackRock Flexible Income ETF 9.1 % iShares 20+ Year Treasury Bond ETF 8.1 % iShares Core S&P 500 ETF 6.0 % iShares Edge Investment Grade Enhanced Bond ETF 5.8 % BlackRock Cash Funds: Institutional, SL Agency Shares 5.1 % iShares S&P 500 Growth ETF 3.7 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000050829 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 60/40 Target Allocation Fund
Class Name	Institutional Shares
Trading Symbol	BIGPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 60/40 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Institutional Shares $ (a) 0.10 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 11	[16]
Expense Ratio, Percent	0.10%	[16]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Institutional Shares returned 23.81% For the same period, the MSCI All Country World Index returned 31.76% and the secondary performance benchmark, a blend of MSCI ACWI Index (42%)/MSCI USA Index (18%)/Bloomberg U.S. Universal Index (40%), returned 24.31%. What contributed to performance? Allocations to U.S. large-cap stocks, the U.S. quality factor, large-cap sustainable stocks, the U.S. large-cap growth factor, and international developed-market equities made the largest contributions. What detracted from performance? Allocations to U.S. mid-cap stocks, inflation-linked U.S. Treasuries, a systematic high yield bond strategy, and the U.S. minimum volatility factor detracted in the time they were held in the Fund. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Institutional Shares 23.81 % 8.73 % 7.37 % MSCI All Country World Index 31.76 12.19 9.39 MSCI ACWI Index (42%)/MSCI USA Index (18%)/Bloomberg U.S. Universal Index (40%) 24.31 8.42 7.29
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 1,678,880,271
Holdings Count \| Holding	21
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	104%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 21 Net Investment Advisory Fees $ Portfolio Turnover Rate 104 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Equity Funds 59.6 % Fixed-Income Funds 37.1 % Short-Term Securities 3.3 % Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 20.1 % BlackRock Total Return Fund, Class K 14.4 % iShares Core Total USD Bond Market ETF 10.4 % iShares S&P 500 Growth ETF 9.6 % iShares MSCI U.S.A. Quality Factor ETF 9.4 % BlackRock U.S. Equity Factor Rotation ETF 9.1 % iShares MSCI EAFE Value ETF 7.7 % BlackRock Strategic Income Opportunities Portfolio, Class K 7.6 % BlackRock U.S. Mortgage Portfolio, Institutional Class 6.4 % iShares S&P 500 Value ETF 5.3 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 20.1 % BlackRock Total Return Fund, Class K 14.4 % iShares Core Total USD Bond Market ETF 10.4 % iShares S&P 500 Growth ETF 9.6 % iShares MSCI U.S.A. Quality Factor ETF 9.4 % BlackRock U.S. Equity Factor Rotation ETF 9.1 % iShares MSCI EAFE Value ETF 7.7 % BlackRock Strategic Income Opportunities Portfolio, Class K 7.6 % BlackRock U.S. Mortgage Portfolio, Institutional Class 6.4 % iShares S&P 500 Value ETF 5.3 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000050830 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 60/40 Target Allocation Fund
Class Name	Investor A Shares
Trading Symbol	BAGPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 60/40 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Investor A Shares $ (a) 0.44 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 49	[17]
Expense Ratio, Percent	0.44%	[17]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Investor A Shares returned 23.41% For the same period, the MSCI All Country World Index returned 31.76% and the secondary performance benchmark, a blend of MSCI ACWI Index (42%)/MSCI USA Index (18%)/Bloomberg U.S. Universal Index (40%), returned 24.31%. What contributed to performance? Allocations to U.S. large-cap stocks, the U.S. quality factor, large-cap sustainable stocks, the U.S. large-cap growth factor, and international developed-market equities made the largest contributions. What detracted from performance? Allocations to U.S. mid-cap stocks, inflation-linked U.S. Treasuries, a systematic high yield bond strategy, and the U.S. minimum volatility factor detracted in the time they were held in the Fund. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Investor A Shares 23.41 % 8.36 % 7.00 % Investor A Shares (with sales charge) 16.93 7.20 6.43 MSCI All Country World Index 31.76 12.19 9.39 MSCI ACWI Index (42%)/MSCI USA Index (18%)/Bloomberg U.S. Universal Index (40%) 24.31 8.42 7.29
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 1,678,880,271
Holdings Count \| Holding	21
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	104%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 21 Net Investment Advisory Fees $ Portfolio Turnover Rate 104 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Equity Funds 59.6 % Fixed-Income Funds 37.1 % Short-Term Securities 3.3 % Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 20.1 % BlackRock Total Return Fund, Class K 14.4 % iShares Core Total USD Bond Market ETF 10.4 % iShares S&P 500 Growth ETF 9.6 % iShares MSCI U.S.A. Quality Factor ETF 9.4 % BlackRock U.S. Equity Factor Rotation ETF 9.1 % iShares MSCI EAFE Value ETF 7.7 % BlackRock Strategic Income Opportunities Portfolio, Class K 7.6 % BlackRock U.S. Mortgage Portfolio, Institutional Class 6.4 % iShares S&P 500 Value ETF 5.3 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 20.1 % BlackRock Total Return Fund, Class K 14.4 % iShares Core Total USD Bond Market ETF 10.4 % iShares S&P 500 Growth ETF 9.6 % iShares MSCI U.S.A. Quality Factor ETF 9.4 % BlackRock U.S. Equity Factor Rotation ETF 9.1 % iShares MSCI EAFE Value ETF 7.7 % BlackRock Strategic Income Opportunities Portfolio, Class K 7.6 % BlackRock U.S. Mortgage Portfolio, Institutional Class 6.4 % iShares S&P 500 Value ETF 5.3 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000050831 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 60/40 Target Allocation Fund
Class Name	Investor C Shares
Trading Symbol	BCGPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 60/40 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Investor C Shares $ (a) 1.18 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 131	[18]
Expense Ratio, Percent	1.18%	[18]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Investor C Shares returned 22.44% For the same period, the MSCI All Country World Index returned 31.76% and the secondary performance benchmark, a blend of MSCI ACWI Index (42%)/MSCI USA Index (18%)/Bloomberg U.S. Universal Index (40%), returned 24.31%. What contributed to performance? Allocations to U.S. large-cap stocks, the U.S. quality factor, large-cap sustainable stocks, the U.S. large-cap growth factor, and international developed-market equities made the largest contributions. What detracted from performance? Allocations to U.S. mid-cap stocks, inflation-linked U.S. Treasuries, a systematic high yield bond strategy, and the U.S. minimum volatility factor detracted in the time they were held in the Fund. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Investor C Shares 22.44 % 7.56 % 6.37 % Investor C Shares (with sales charge) 21.44 7.56 6.37 MSCI All Country World Index 31.76 12.19 9.39 MSCI ACWI Index (42%)/MSCI USA Index (18%)/Bloomberg U.S. Universal Index (40%) 24.31 8.42 7.29
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 1,678,880,271
Holdings Count \| Holding	21
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	104%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 21 Net Investment Advisory Fees $ Portfolio Turnover Rate 104 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Equity Funds 59.6 % Fixed-Income Funds 37.1 % Short-Term Securities 3.3 % Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 20.1 % BlackRock Total Return Fund, Class K 14.4 % iShares Core Total USD Bond Market ETF 10.4 % iShares S&P 500 Growth ETF 9.6 % iShares MSCI U.S.A. Quality Factor ETF 9.4 % BlackRock U.S. Equity Factor Rotation ETF 9.1 % iShares MSCI EAFE Value ETF 7.7 % BlackRock Strategic Income Opportunities Portfolio, Class K 7.6 % BlackRock U.S. Mortgage Portfolio, Institutional Class 6.4 % iShares S&P 500 Value ETF 5.3 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 20.1 % BlackRock Total Return Fund, Class K 14.4 % iShares Core Total USD Bond Market ETF 10.4 % iShares S&P 500 Growth ETF 9.6 % iShares MSCI U.S.A. Quality Factor ETF 9.4 % BlackRock U.S. Equity Factor Rotation ETF 9.1 % iShares MSCI EAFE Value ETF 7.7 % BlackRock Strategic Income Opportunities Portfolio, Class K 7.6 % BlackRock U.S. Mortgage Portfolio, Institutional Class 6.4 % iShares S&P 500 Value ETF 5.3 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000166013 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 60/40 Target Allocation Fund
Class Name	Class K Shares
Trading Symbol	BKGPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 60/40 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Class K Shares $ (a) 0.08 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 9	[19]
Expense Ratio, Percent	0.08%	[19]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Class K Shares returned 23.84% For the same period, the MSCI All Country World Index returned 31.76% and the secondary performance benchmark, a blend of MSCI ACWI Index (42%)/MSCI USA Index (18%)/Bloomberg U.S. Universal Index (40%), returned 24.31%. What contributed to performance? Allocations to U.S. large-cap stocks, the U.S. quality factor, large-cap sustainable stocks, the U.S. large-cap growth factor, and international developed-market equities made the largest contributions. What detracted from performance? Allocations to U.S. mid-cap stocks, inflation-linked U.S. Treasuries, a systematic high yield bond strategy, and the U.S. minimum volatility factor detracted in the time they were held in the Fund. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Class K Shares 23.84 % 8.75 % 7.39 % MSCI All Country World Index 31.76 12.19 9.39 MSCI ACWI Index (42%)/MSCI USA Index (18%)/Bloomberg U.S. Universal Index (40%) 24.31 8.42 7.29
Performance Inception Date	Mar. 28, 2016
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 1,678,880,271
Holdings Count \| Holding	21
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	104%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 21 Net Investment Advisory Fees $ Portfolio Turnover Rate 104 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Equity Funds 59.6 % Fixed-Income Funds 37.1 % Short-Term Securities 3.3 % Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 20.1 % BlackRock Total Return Fund, Class K 14.4 % iShares Core Total USD Bond Market ETF 10.4 % iShares S&P 500 Growth ETF 9.6 % iShares MSCI U.S.A. Quality Factor ETF 9.4 % BlackRock U.S. Equity Factor Rotation ETF 9.1 % iShares MSCI EAFE Value ETF 7.7 % BlackRock Strategic Income Opportunities Portfolio, Class K 7.6 % BlackRock U.S. Mortgage Portfolio, Institutional Class 6.4 % iShares S&P 500 Value ETF 5.3 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 20.1 % BlackRock Total Return Fund, Class K 14.4 % iShares Core Total USD Bond Market ETF 10.4 % iShares S&P 500 Growth ETF 9.6 % iShares MSCI U.S.A. Quality Factor ETF 9.4 % BlackRock U.S. Equity Factor Rotation ETF 9.1 % iShares MSCI EAFE Value ETF 7.7 % BlackRock Strategic Income Opportunities Portfolio, Class K 7.6 % BlackRock U.S. Mortgage Portfolio, Institutional Class 6.4 % iShares S&P 500 Value ETF 5.3 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports
C000050832 [Member]
Shareholder Report [Line Items]
Fund Name	BlackRock 60/40 Target Allocation Fund
Class Name	Class R Shares
Trading Symbol	BRGPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about BlackRock 60/40 Target Allocation Fund (the “Fund”) for the period of October 1, 2023 to September 30, 2024.
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
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	(800) 441‑7762
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 Costs paid as a percentage of a Class R Shares $ (a) 0.62 % (a) (a) Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.
Expenses Paid, Amount	$ 69	[20]
Expense Ratio, Percent	0.62%	[20]
Factors Affecting Performance [Text Block]	How did the Fund perform last year? For the reporting period ended September 30, 2024, the Fund's Class R Shares returned 23.19% For the same period, the MSCI All Country World Index returned 31.76% and the secondary performance benchmark, a blend of MSCI ACWI Index (42%)/MSCI USA Index (18%)/Bloomberg U.S. Universal Index (40%), returned 24.31%. What contributed to performance? Allocations to U.S. large-cap stocks, the U.S. quality factor, large-cap sustainable stocks, the U.S. large-cap growth factor, and international developed-market equities made the largest contributions. What detracted from performance? Allocations to U.S. mid-cap stocks, inflation-linked U.S. Treasuries, a systematic high yield bond strategy, and the U.S. minimum volatility factor detracted in the time they were held in the Fund. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.
Performance Past Does Not Indicate Future [Text]	Past performance is not an indication of future results.
Line Graph [Table Text Block]	Fund performance Cumulative performance: October 1, 2014 through September 30, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance.
Average Annual Return [Table Text Block]	Average annual total returns 1 Year 5 Years 10 Years Class R Shares 23.19 % 8.17 % 6.80 % MSCI All Country World Index 31.76 12.19 9.39 MSCI ACWI Index (42%)/MSCI USA Index (18%)/Bloomberg U.S. Universal Index (40%) 24.31 8.42 7.29
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.
Material Change Date	Aug. 28, 2024
Updated Performance Information Location [Text Block]	Visit blackrock.com
Net Assets	$ 1,678,880,271
Holdings Count \| Holding	21
Advisory Fees Paid, Amount	$ 0
Investment Company Portfolio Turnover	104%
Additional Fund Statistics [Text Block]	Key Fund statistics Net Assets $ Number of Portfolio Holdings 21 Net Investment Advisory Fees $ Portfolio Turnover Rate 104 %
Holdings [Text Block]	What did the Fund invest in? (as of September 30, 2024) Portfolio composition Investment Type Percent of Total Equity Funds 59.6 % Fixed-Income Funds 37.1 % Short-Term Securities 3.3 % Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 20.1 % BlackRock Total Return Fund, Class K 14.4 % iShares Core Total USD Bond Market ETF 10.4 % iShares S&P 500 Growth ETF 9.6 % iShares MSCI U.S.A. Quality Factor ETF 9.4 % BlackRock U.S. Equity Factor Rotation ETF 9.1 % iShares MSCI EAFE Value ETF 7.7 % BlackRock Strategic Income Opportunities Portfolio, Class K 7.6 % BlackRock U.S. Mortgage Portfolio, Institutional Class 6.4 % iShares S&P 500 Value ETF 5.3 % (a) Excludes short-term securities.
Largest Holdings [Text Block]	Ten largest holdings Security Percent of Total (a) iShares Core S&P 500 ETF 20.1 % BlackRock Total Return Fund, Class K 14.4 % iShares Core Total USD Bond Market ETF 10.4 % iShares S&P 500 Growth ETF 9.6 % iShares MSCI U.S.A. Quality Factor ETF 9.4 % BlackRock U.S. Equity Factor Rotation ETF 9.1 % iShares MSCI EAFE Value ETF 7.7 % BlackRock Strategic Income Opportunities Portfolio, Class K 7.6 % BlackRock U.S. Mortgage Portfolio, Institutional Class 6.4 % iShares S&P 500 Value ETF 5.3 % (a) Excludes short-term securities.
Material Fund Change [Text Block]	Material Fund changes This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after September 30, 2024 at blackrock.com/fundreports Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Material Fund Change Expenses [Text Block]	Effective August 28, 2024, BlackRock Advisors, LLC, the Fund’s investment adviser, contractually agreed to reimburse the Fund for certain expenses associated with the Fund’s investment in the BlackRock Total Return Fund, a series of BlackRock Bond Fund, Inc. through June 30, 2026. The reimbursement amount is calculated as the product of (i) the daily market value of the Fund’s assets invested in BlackRock Total Return Fund and (ii) the difference between (a) the total expenses after fees waived and/or reimbursed of Class K Shares in BlackRock Total Return Fund’s most recent annual or semiannual report and (b) 0.06%, divided by the number of days in the calendar year.
Updated Prospectus Phone Number	(800) 441-7762
Updated Prospectus Web Address	blackrock.com/fundreports

[1]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[2]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[3]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[4]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[5]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[6]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[7]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[8]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[9]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[10]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[11]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[12]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[13]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[14]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[15]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[16]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[17]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[18]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[19]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.[20]Excludes fees and expenses incurred indirectly as a result of investments in underlying funds.

Shareholder Report, Line Graph

Shareholder Report, Line Graph (Details) - USD ($)	12 Months Ended	60 Months Ended	120 Months Ended
Shareholder Report, Line Graph (Details) - USD ($)	Sep. 30, 2024	Sep. 30, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
C000050684 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Institutional Shares
Account Value	$ 23,375	$ 23,375	$ 23,375	$ 18,312	$ 15,713	$ 19,167	$ 15,550	$ 13,748	$ 13,372	$ 12,195	$ 10,687	$ 9,866	$ 10,000
Average Annual Return, Percent	27.65%	11.20%	8.86%
C000050685 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Investor A Shares (with sales charge)
Average Annual Return, Percent	20.66%	9.65%	7.91%
C000050685 [Member] \| Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Investor A Shares
Account Value	$ 21,411	$ 21,411	$ 21,411	16,813	14,485	17,735	14,428	12,799	12,500	11,434	10,060	9,314	9,475
Average Annual Return, Percent	27.34%	10.84%	8.49%
C000050686 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Investor C Shares (with sales charge)
Average Annual Return, Percent	25.36%	10.01%	7.85%
C000050686 [Member] \| Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Investor C Shares
Account Value	$ 21,283	$ 21,283	$ 21,283	16,713	14,399	17,758	14,562	13,013	12,804	11,796	10,457	9,761	10,000
Average Annual Return, Percent	26.36%	10.01%	7.85%
C000166010 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Class K Shares
Account Value	$ 23,418	$ 23,418	$ 23,418	18,332	15,729	19,193	15,560	13,754	13,375	12,196	10,697	9,866	10,000
Average Annual Return, Percent	27.74%	11.23%	8.88%
C000050687 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Class R Shares
Account Value	$ 22,233	$ 22,233	$ 22,233	17,494	15,091	18,501	15,079	13,399	13,108	12,010	10,577	9,811	10,000
Average Annual Return, Percent	27.09%	10.66%	8.32%
C000050742 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Institutional Shares
Account Value	$ 17,690	$ 17,690	$ 17,690	14,757	13,638	16,236	14,380	13,017	12,280	11,724	10,807	10,166	10,000
Average Annual Return, Percent	19.88%	6.33%	5.87%
C000050743 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Investor A Shares (with sales charge)
Average Annual Return, Percent	13.20%	4.84%	4.95%
C000050743 [Member] \| Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Investor A Shares
Account Value	$ 16,207.36	$ 16,207.36	$ 16,207.36	13,566.36	12,570.42	15,019.4	13,352.52	12,122.11	11,482.63	10,996.62	10,166.3	9,600.71	9,475
Average Annual Return, Percent	19.47%	5.98%	5.51%
C000050744 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Investor C Shares (with sales charge)
Average Annual Return, Percent	17.58%	5.18%	4.89%
C000050744 [Member] \| Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Investor C Shares
Account Value	$ 16,114.47	$ 16,114.47	$ 16,114.47	13,488.6	12,498.37	15,045.22	13,472.04	12,326.3	11,754	11,352	10,577.87	10,056.86	10,000
Average Annual Return, Percent	18.58%	5.18%	4.89%
C000166011 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Class K Shares
Account Value	$ 17,725.47	$ 17,725.47	$ 17,725.47	14,785.62	13,661.55	16,259.65	14,399.81	13,032.96	12,293.1	11,735.42	10,817.03	10,165.57	10,000
Average Annual Return, Percent	19.88%	6.34%	5.89%
C000050745 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Class R Shares
Account Value	$ 16,831	$ 16,831	$ 16,831	14,113	13,105	15,675	13,962	12,694	12,038	11,555	10,705	10,117	10,000
Average Annual Return, Percent	19.26%	5.80%	5.34%
C000050785 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Institutional Shares
Account Value	$ 14,758	$ 14,758	$ 14,758	12,682	12,157	14,423	13,391	12,450	11,610	11,353	10,803	10,312	10,000
Average Annual Return, Percent	16.37%	3.46%	3.97%
C000050786 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Investor A Shares (with sales charge)
Average Annual Return, Percent	9.97%	2.03%	3.07%
C000050786 [Member] \| Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Investor A Shares
Account Value	$ 13,527	$ 13,527	$ 13,527	11,655	11,207	13,351	12,436	11,593	10,852	10,646	10,161	9,737	9,475
Average Annual Return, Percent	16.06%	3.13%	3.62%
C000050787 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Investor C Shares (with sales charge)
Average Annual Return, Percent	14.08%	2.34%	3.02%
C000050787 [Member] \| Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Investor C Shares
Account Value	$ 13,468	$ 13,468	$ 13,468	11,604	11,158	13,372	12,550	11,798	11,120	10,994	10,571	10,200	10,000
Average Annual Return, Percent	15.08%	2.34%	3.02%
C000166012 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Class K Shares
Account Value	$ 14,781	$ 14,781	$ 14,781	12,699	12,170	14,436	13,402	12,458	11,615	11,355	10,803	10,312	10,000
Average Annual Return, Percent	16.39%	3.48%	3.99%
C000050788 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Class R Shares
Account Value	$ 13,865	$ 13,865	$ 13,865	11,985	11,555	13,807	12,895	12,066	11,322	11,139	10,671	10,250	10,000
Average Annual Return, Percent	15.69%	2.82%	3.32%
C000050829 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Institutional Shares
Account Value	$ 20,363.95	$ 20,363.95	$ 20,363.95	16,446.93	14,637.36	17,699.2	15,007.13	13,399.29	12,856.56	11,968.53	10,763.82	10,042.16	10,000
Average Annual Return, Percent	23.81%	8.73%	7.37%
C000050830 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Investor A Shares (with sales charge)
Average Annual Return, Percent	16.93%	7.20%	6.43%
C000050830 [Member] \| Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Investor A Shares
Account Value	$ 18,643.59	$ 18,643.59	$ 18,643.59	15,106.86	13,490.78	16,363.58	13,917.23	12,476.89	12,004.12	11,215.81	10,116.88	9,475.23	9,475.01
Average Annual Return, Percent	23.41%	8.36%	7%
C000050831 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Investor C Shares (with sales charge)
Average Annual Return, Percent	21.44%	7.56%	6.37%
C000050831 [Member] \| Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Investor C Shares
Account Value	$ 18,540.06	$ 18,540.06	$ 18,540.06	15,022.96	13,415.86	16,397.65	14,046.37	12,689.77	12,302.86	11,581.22	10,522.38	9,936.93	10,000
Average Annual Return, Percent	22.44%	7.56%	6.37%
C000166013 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Class K Shares
Account Value	$ 20,393.43	$ 20,393.43	$ 20,393.43	16,467.74	14,652.7	17,714.33	15,017.24	13,405.82	12,860.43	11,970.17	10,754.91	10,042.16	10,000
Average Annual Return, Percent	23.84%	8.75%	7.39%
C000050832 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Class R Shares
Account Value	$ 19,309.84	$ 19,309.84	$ 19,309.84	15,674.66	14,030.58	17,045.65	14,530.81	13,041.61	12,578.84	11,772.86	10,645.38	9,983.66	10,000
Average Annual Return, Percent	23.19%	8.17%	6.80%
MSCI All Country World C000050686 Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	MSCI All Country World Index
Average Annual Return, Percent	31.76%	12.19%	9.39%
MSCI All Country World C000050684 Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	MSCI All Country World Index
Average Annual Return, Percent	31.76%	12.19%	9.39%
MSCI All Country World C000166010 Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	MSCI All Country World Index
Average Annual Return, Percent	31.76%	12.19%	9.39%
MSCI All Country World C000050685 Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	MSCI All Country World Index
Average Annual Return, Percent	31.76%	12.19%	9.39%
MSCI All Country World C000050687 Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	MSCI All Country World Index
Average Annual Return, Percent	31.76%	12.19%	9.39%
Bloomberg U S Universal Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	Bloomberg U.S. Universal Index
Account Value	$ 12,373	$ 12,373	$ 12,373	11,040	10,865	12,771	12,745	11,946	10,853	10,963	10,859	10,233	10,000
Average Annual Return, Percent	12.08%	0.70%	2.15%
MSCI All Country World C000050829 Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	MSCI All Country World Index
Average Annual Return, Percent	31.76%	12.19%	9.39%
MSCI All Country World C000050830 Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	MSCI All Country World Index
Average Annual Return, Percent	31.76%	12.19%	9.39%
MSCI All Country World C000050832 Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	MSCI All Country World Index
Average Annual Return, Percent	31.76%	12.19%	9.39%
MSCI All Country World C000050831 Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	MSCI All Country World Index
Average Annual Return, Percent	31.76%	12.19%	9.39%
MSCI All Country World C000166013 Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	MSCI All Country World Index
Average Annual Return, Percent	31.76%	12.19%	9.39%
MSCI ACWI Index 56 MSCI USA Index 24 Bloomberg U S Universal Index 20 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	MSCI ACWI Index (56%)/MSCI USA Index (24%)/Bloomberg U.S. Universal Index (20%)
Account Value	$ 23,407	$ 23,407	$ 23,407	18,206	15,579	19,154	15,667	13,996	13,478	12,331	10,747	9,648	10,000
Average Annual Return, Percent	28.57%	10.83%	8.88%
MSCI ACWI Index 28 MSCI USA Index 12 Bloomberg U S Universal Index 60 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	MSCI ACWI Index (28%)/MSCI USA Index (12%)/Bloomberg U.S. Universal Index (60%)
Account Value	$ 17,314	$ 17,314	$ 17,314	14,411	13,213	15,858	14,300	12,991	12,122	11,648	10,816	9,944	10,000
Average Annual Return, Percent	20.14%	5.91%	5.64%
MSCI All Country World Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	MSCI All Country World Index
Account Value	$ 24,526	$ 24,526	$ 24,526	18,615	15,409	19,421	15,240	13,799	13,611	12,399	10,451	9,334	10,000
Average Annual Return, Percent	31.76%	12.19%	9.39%
MSCI ACWI Index 14 MSCI USA Index 6 Bloomberg U S Universal Index 80 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	MSCI ACWI Index (14%)/MSCI USA Index (6%)/Bloomberg U.S. Universal Index (80%)
Account Value	$ 14,698	$ 14,698	$ 14,698	12,664	12,027	14,279	13,539	12,472	11,476	11,305	10,841	10,090	10,000
Average Annual Return, Percent	16.06%	3.34%	3.93%
MSCI ACWI Index 42 MSCI USA Index 18 Bloomberg U S Universal Index 40 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name	MSCI ACWI Index (42%)/MSCI USA Index (18%)/Bloomberg U.S. Universal Index (40%)
Account Value	$ 20,220	$ 20,220	$ 20,220	$ 16,266	$ 14,405	$ 17,491	$ 15,015	$ 13,500	$ 12,789	$ 11,990	$ 10,785	$ 9,797	$ 10,000
Average Annual Return, Percent	24.31%	8.42%	7.29%

Shareholder Report, Holdings (D

Shareholder Report, Holdings (Details)	Sep. 30, 2024
C000050684 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	23.50%	[1]
C000050684 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	12.60%	[1]
C000050684 [Member] \| iShares MSCI U S A Quality Factor ETF [Member]
Holdings [Line Items]
Percent of Total Investments	11.10%	[1]
C000050684 [Member] \| BlackRock U S Equity Factor Rotation ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.60%	[1]
C000050684 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%	[1]
C000050684 [Member] \| iShares MSCI EAFE Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%	[1]
C000050684 [Member] \| iShares MSCI EAFE Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.40%	[1]
C000050684 [Member] \| iShares S And P 500 Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.40%	[1]
C000050684 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	6.10%	[1]
C000050684 [Member] \| iShares MSCI Emerging Markets ex China ETF [Member]
Holdings [Line Items]
Percent of Total Investments	4.70%	[1]
C000050684 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	18%
C000050684 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000050684 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	78.90%
C000050685 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	23.50%	[2]
C000050685 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	12.60%	[2]
C000050685 [Member] \| iShares MSCI U S A Quality Factor ETF [Member]
Holdings [Line Items]
Percent of Total Investments	11.10%	[2]
C000050685 [Member] \| BlackRock U S Equity Factor Rotation ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.60%	[2]
C000050685 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%	[2]
C000050685 [Member] \| iShares MSCI EAFE Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%	[2]
C000050685 [Member] \| iShares MSCI EAFE Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.40%	[2]
C000050685 [Member] \| iShares S And P 500 Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.40%	[2]
C000050685 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	6.10%	[2]
C000050685 [Member] \| iShares MSCI Emerging Markets ex China ETF [Member]
Holdings [Line Items]
Percent of Total Investments	4.70%	[2]
C000050685 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	18%
C000050685 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000050685 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	78.90%
C000050686 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	23.50%	[3]
C000050686 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	12.60%	[3]
C000050686 [Member] \| iShares MSCI U S A Quality Factor ETF [Member]
Holdings [Line Items]
Percent of Total Investments	11.10%	[3]
C000050686 [Member] \| BlackRock U S Equity Factor Rotation ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.60%	[3]
C000050686 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%	[3]
C000050686 [Member] \| iShares MSCI EAFE Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%	[3]
C000050686 [Member] \| iShares MSCI EAFE Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.40%	[3]
C000050686 [Member] \| iShares S And P 500 Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.40%	[3]
C000050686 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	6.10%	[3]
C000050686 [Member] \| iShares MSCI Emerging Markets ex China ETF [Member]
Holdings [Line Items]
Percent of Total Investments	4.70%	[3]
C000050686 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	18%
C000050686 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000050686 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	78.90%
C000166010 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	23.50%	[4]
C000166010 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	12.60%	[4]
C000166010 [Member] \| iShares MSCI U S A Quality Factor ETF [Member]
Holdings [Line Items]
Percent of Total Investments	11.10%	[4]
C000166010 [Member] \| BlackRock U S Equity Factor Rotation ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.60%	[4]
C000166010 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%	[4]
C000166010 [Member] \| iShares MSCI EAFE Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%	[4]
C000166010 [Member] \| iShares MSCI EAFE Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.40%	[4]
C000166010 [Member] \| iShares S And P 500 Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.40%	[4]
C000166010 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	6.10%	[4]
C000166010 [Member] \| iShares MSCI Emerging Markets ex China ETF [Member]
Holdings [Line Items]
Percent of Total Investments	4.70%	[4]
C000166010 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	18%
C000166010 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000166010 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	78.90%
C000050687 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	23.50%	[5]
C000050687 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	12.60%	[5]
C000050687 [Member] \| iShares MSCI U S A Quality Factor ETF [Member]
Holdings [Line Items]
Percent of Total Investments	11.10%	[5]
C000050687 [Member] \| BlackRock U S Equity Factor Rotation ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.60%	[5]
C000050687 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%	[5]
C000050687 [Member] \| iShares MSCI EAFE Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%	[5]
C000050687 [Member] \| iShares MSCI EAFE Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.40%	[5]
C000050687 [Member] \| iShares S And P 500 Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.40%	[5]
C000050687 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	6.10%	[5]
C000050687 [Member] \| iShares MSCI Emerging Markets ex China ETF [Member]
Holdings [Line Items]
Percent of Total Investments	4.70%	[5]
C000050687 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	18%
C000050687 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000050687 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	78.90%
C000050742 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	13.60%	[6]
C000050742 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7%	[6]
C000050742 [Member] \| iShares MSCI U S A Quality Factor ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%	[6]
C000050742 [Member] \| BlackRock U S Equity Factor Rotation ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6.50%	[6]
C000050742 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	15.60%	[6]
C000050742 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	18.20%	[6]
C000050742 [Member] \| BlackRock Strategic Income Opportunities Portfolio Class K [Member]
Holdings [Line Items]
Percent of Total Investments	10.40%	[6]
C000050742 [Member] \| BlackRock U S Mortgage Portfolio Institutional Class [Member]
Holdings [Line Items]
Percent of Total Investments	7.80%	[6]
C000050742 [Member] \| BlackRock Flexible Income ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.60%	[6]
C000050742 [Member] \| iShares 20 Year Treasury Bond ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6.50%	[6]
C000050742 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	55.60%
C000050742 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000050742 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	39.90%
C000050743 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	13.60%	[7]
C000050743 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7%	[7]
C000050743 [Member] \| iShares MSCI U S A Quality Factor ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%	[7]
C000050743 [Member] \| BlackRock U S Equity Factor Rotation ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6.50%	[7]
C000050743 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	15.60%	[7]
C000050743 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	18.20%	[7]
C000050743 [Member] \| BlackRock Strategic Income Opportunities Portfolio Class K [Member]
Holdings [Line Items]
Percent of Total Investments	10.40%	[7]
C000050743 [Member] \| BlackRock U S Mortgage Portfolio Institutional Class [Member]
Holdings [Line Items]
Percent of Total Investments	7.80%	[7]
C000050743 [Member] \| BlackRock Flexible Income ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.60%	[7]
C000050743 [Member] \| iShares 20 Year Treasury Bond ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6.50%	[7]
C000050743 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	55.60%
C000050743 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000050743 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	39.90%
C000050744 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	13.60%	[8]
C000050744 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7%	[8]
C000050744 [Member] \| iShares MSCI U S A Quality Factor ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%	[8]
C000050744 [Member] \| BlackRock U S Equity Factor Rotation ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6.50%	[8]
C000050744 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	15.60%	[8]
C000050744 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	18.20%	[8]
C000050744 [Member] \| BlackRock Strategic Income Opportunities Portfolio Class K [Member]
Holdings [Line Items]
Percent of Total Investments	10.40%	[8]
C000050744 [Member] \| BlackRock U S Mortgage Portfolio Institutional Class [Member]
Holdings [Line Items]
Percent of Total Investments	7.80%	[8]
C000050744 [Member] \| BlackRock Flexible Income ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.60%	[8]
C000050744 [Member] \| iShares 20 Year Treasury Bond ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6.50%	[8]
C000050744 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	55.60%
C000050744 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000050744 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	39.90%
C000166011 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	13.60%	[9]
C000166011 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7%	[9]
C000166011 [Member] \| iShares MSCI U S A Quality Factor ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%	[9]
C000166011 [Member] \| BlackRock U S Equity Factor Rotation ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6.50%	[9]
C000166011 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	15.60%	[9]
C000166011 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	18.20%	[9]
C000166011 [Member] \| BlackRock Strategic Income Opportunities Portfolio Class K [Member]
Holdings [Line Items]
Percent of Total Investments	10.40%	[9]
C000166011 [Member] \| BlackRock U S Mortgage Portfolio Institutional Class [Member]
Holdings [Line Items]
Percent of Total Investments	7.80%	[9]
C000166011 [Member] \| BlackRock Flexible Income ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.60%	[9]
C000166011 [Member] \| iShares 20 Year Treasury Bond ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6.50%	[9]
C000166011 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	55.60%
C000166011 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000166011 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	39.90%
C000050745 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	13.60%	[10]
C000050745 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7%	[10]
C000050745 [Member] \| iShares MSCI U S A Quality Factor ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%	[10]
C000050745 [Member] \| BlackRock U S Equity Factor Rotation ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6.50%	[10]
C000050745 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	15.60%	[10]
C000050745 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	18.20%	[10]
C000050745 [Member] \| BlackRock Strategic Income Opportunities Portfolio Class K [Member]
Holdings [Line Items]
Percent of Total Investments	10.40%	[10]
C000050745 [Member] \| BlackRock U S Mortgage Portfolio Institutional Class [Member]
Holdings [Line Items]
Percent of Total Investments	7.80%	[10]
C000050745 [Member] \| BlackRock Flexible Income ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.60%	[10]
C000050745 [Member] \| iShares 20 Year Treasury Bond ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6.50%	[10]
C000050745 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	55.60%
C000050745 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000050745 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	39.90%
C000050785 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6%	[11]
C000050785 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	3.70%	[11]
C000050785 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	19.60%	[11]
C000050785 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	19.60%	[11]
C000050785 [Member] \| BlackRock Strategic Income Opportunities Portfolio Class K [Member]
Holdings [Line Items]
Percent of Total Investments	13.80%	[11]
C000050785 [Member] \| BlackRock U S Mortgage Portfolio Institutional Class [Member]
Holdings [Line Items]
Percent of Total Investments	9.20%	[11]
C000050785 [Member] \| BlackRock Flexible Income ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%	[11]
C000050785 [Member] \| iShares 20 Year Treasury Bond ETF [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%	[11]
C000050785 [Member] \| iShares Edge Investment Grade Enhanced Bond ETF [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%	[11]
C000050785 [Member] \| BlackRock Cash Funds Institutional SL Agency Shares [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%	[11]
C000050785 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	75.10%
C000050785 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	4.40%
C000050785 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	20.50%
C000050786 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6%	[12]
C000050786 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	3.70%	[12]
C000050786 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	19.60%	[12]
C000050786 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	19.60%	[12]
C000050786 [Member] \| BlackRock Strategic Income Opportunities Portfolio Class K [Member]
Holdings [Line Items]
Percent of Total Investments	13.80%	[12]
C000050786 [Member] \| BlackRock U S Mortgage Portfolio Institutional Class [Member]
Holdings [Line Items]
Percent of Total Investments	9.20%	[12]
C000050786 [Member] \| BlackRock Flexible Income ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%	[12]
C000050786 [Member] \| iShares 20 Year Treasury Bond ETF [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%	[12]
C000050786 [Member] \| iShares Edge Investment Grade Enhanced Bond ETF [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%	[12]
C000050786 [Member] \| BlackRock Cash Funds Institutional SL Agency Shares [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%	[12]
C000050786 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	75.10%
C000050786 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	4.40%
C000050786 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	20.50%
C000050787 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6%	[13]
C000050787 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	3.70%	[13]
C000050787 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	19.60%	[13]
C000050787 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	19.60%	[13]
C000050787 [Member] \| BlackRock Strategic Income Opportunities Portfolio Class K [Member]
Holdings [Line Items]
Percent of Total Investments	13.80%	[13]
C000050787 [Member] \| BlackRock U S Mortgage Portfolio Institutional Class [Member]
Holdings [Line Items]
Percent of Total Investments	9.20%	[13]
C000050787 [Member] \| BlackRock Flexible Income ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%	[13]
C000050787 [Member] \| iShares 20 Year Treasury Bond ETF [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%	[13]
C000050787 [Member] \| iShares Edge Investment Grade Enhanced Bond ETF [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%	[13]
C000050787 [Member] \| BlackRock Cash Funds Institutional SL Agency Shares [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%	[13]
C000050787 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	75.10%
C000050787 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	4.40%
C000050787 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	20.50%
C000166012 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6%	[14]
C000166012 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	3.70%	[14]
C000166012 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	19.60%	[14]
C000166012 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	19.60%	[14]
C000166012 [Member] \| BlackRock Strategic Income Opportunities Portfolio Class K [Member]
Holdings [Line Items]
Percent of Total Investments	13.80%	[14]
C000166012 [Member] \| BlackRock U S Mortgage Portfolio Institutional Class [Member]
Holdings [Line Items]
Percent of Total Investments	9.20%	[14]
C000166012 [Member] \| BlackRock Flexible Income ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%	[14]
C000166012 [Member] \| iShares 20 Year Treasury Bond ETF [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%	[14]
C000166012 [Member] \| iShares Edge Investment Grade Enhanced Bond ETF [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%	[14]
C000166012 [Member] \| BlackRock Cash Funds Institutional SL Agency Shares [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%	[14]
C000166012 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	75.10%
C000166012 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	4.40%
C000166012 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	20.50%
C000050788 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	6%	[15]
C000050788 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	3.70%	[15]
C000050788 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	19.60%	[15]
C000050788 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	19.60%	[15]
C000050788 [Member] \| BlackRock Strategic Income Opportunities Portfolio Class K [Member]
Holdings [Line Items]
Percent of Total Investments	13.80%	[15]
C000050788 [Member] \| BlackRock U S Mortgage Portfolio Institutional Class [Member]
Holdings [Line Items]
Percent of Total Investments	9.20%	[15]
C000050788 [Member] \| BlackRock Flexible Income ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%	[15]
C000050788 [Member] \| iShares 20 Year Treasury Bond ETF [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%	[15]
C000050788 [Member] \| iShares Edge Investment Grade Enhanced Bond ETF [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%	[15]
C000050788 [Member] \| BlackRock Cash Funds Institutional SL Agency Shares [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%	[15]
C000050788 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	75.10%
C000050788 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	4.40%
C000050788 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	20.50%
C000050829 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	20.10%	[16]
C000050829 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.60%	[16]
C000050829 [Member] \| iShares MSCI U S A Quality Factor ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%	[16]
C000050829 [Member] \| BlackRock U S Equity Factor Rotation ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%	[16]
C000050829 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	10.40%	[16]
C000050829 [Member] \| iShares MSCI EAFE Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.70%	[16]
C000050829 [Member] \| iShares S And P 500 Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	5.30%	[16]
C000050829 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%	[16]
C000050829 [Member] \| BlackRock Strategic Income Opportunities Portfolio Class K [Member]
Holdings [Line Items]
Percent of Total Investments	7.60%	[16]
C000050829 [Member] \| BlackRock U S Mortgage Portfolio Institutional Class [Member]
Holdings [Line Items]
Percent of Total Investments	6.40%	[16]
C000050829 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	37.10%
C000050829 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	3.30%
C000050829 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	59.60%
C000050830 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	20.10%	[17]
C000050830 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.60%	[17]
C000050830 [Member] \| iShares MSCI U S A Quality Factor ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%	[17]
C000050830 [Member] \| BlackRock U S Equity Factor Rotation ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%	[17]
C000050830 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	10.40%	[17]
C000050830 [Member] \| iShares MSCI EAFE Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.70%	[17]
C000050830 [Member] \| iShares S And P 500 Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	5.30%	[17]
C000050830 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%	[17]
C000050830 [Member] \| BlackRock Strategic Income Opportunities Portfolio Class K [Member]
Holdings [Line Items]
Percent of Total Investments	7.60%	[17]
C000050830 [Member] \| BlackRock U S Mortgage Portfolio Institutional Class [Member]
Holdings [Line Items]
Percent of Total Investments	6.40%	[17]
C000050830 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	37.10%
C000050830 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	3.30%
C000050830 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	59.60%
C000050831 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	20.10%	[18]
C000050831 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.60%	[18]
C000050831 [Member] \| iShares MSCI U S A Quality Factor ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%	[18]
C000050831 [Member] \| BlackRock U S Equity Factor Rotation ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%	[18]
C000050831 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	10.40%	[18]
C000050831 [Member] \| iShares MSCI EAFE Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.70%	[18]
C000050831 [Member] \| iShares S And P 500 Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	5.30%	[18]
C000050831 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%	[18]
C000050831 [Member] \| BlackRock Strategic Income Opportunities Portfolio Class K [Member]
Holdings [Line Items]
Percent of Total Investments	7.60%	[18]
C000050831 [Member] \| BlackRock U S Mortgage Portfolio Institutional Class [Member]
Holdings [Line Items]
Percent of Total Investments	6.40%	[18]
C000050831 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	37.10%
C000050831 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	3.30%
C000050831 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	59.60%
C000166013 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	20.10%	[19]
C000166013 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.60%	[19]
C000166013 [Member] \| iShares MSCI U S A Quality Factor ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%	[19]
C000166013 [Member] \| BlackRock U S Equity Factor Rotation ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%	[19]
C000166013 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	10.40%	[19]
C000166013 [Member] \| iShares MSCI EAFE Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.70%	[19]
C000166013 [Member] \| iShares S And P 500 Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	5.30%	[19]
C000166013 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%	[19]
C000166013 [Member] \| BlackRock Strategic Income Opportunities Portfolio Class K [Member]
Holdings [Line Items]
Percent of Total Investments	7.60%	[19]
C000166013 [Member] \| BlackRock U S Mortgage Portfolio Institutional Class [Member]
Holdings [Line Items]
Percent of Total Investments	6.40%	[19]
C000166013 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	37.10%
C000166013 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	3.30%
C000166013 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	59.60%
C000050832 [Member] \| iShares Core S And P 500 ETF [Member]
Holdings [Line Items]
Percent of Total Investments	20.10%	[20]
C000050832 [Member] \| iShares S And P 500 Growth ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.60%	[20]
C000050832 [Member] \| iShares MSCI U S A Quality Factor ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%	[20]
C000050832 [Member] \| BlackRock U S Equity Factor Rotation ETF [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%	[20]
C000050832 [Member] \| iShares Core Total USD Bond Market ETF [Member]
Holdings [Line Items]
Percent of Total Investments	10.40%	[20]
C000050832 [Member] \| iShares MSCI EAFE Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	7.70%	[20]
C000050832 [Member] \| iShares S And P 500 Value ETF [Member]
Holdings [Line Items]
Percent of Total Investments	5.30%	[20]
C000050832 [Member] \| BlackRock Total Return Fund Class K [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%	[20]
C000050832 [Member] \| BlackRock Strategic Income Opportunities Portfolio Class K [Member]
Holdings [Line Items]
Percent of Total Investments	7.60%	[20]
C000050832 [Member] \| BlackRock U S Mortgage Portfolio Institutional Class [Member]
Holdings [Line Items]
Percent of Total Investments	6.40%	[20]
C000050832 [Member] \| Fixed Income Funds [Member]
Holdings [Line Items]
Percent of Total Investments	37.10%
C000050832 [Member] \| Short Term Securities [Member]
Holdings [Line Items]
Percent of Total Investments	3.30%
C000050832 [Member] \| Equity Funds Securities [Member]
Holdings [Line Items]
Percent of Total Investments	59.60%

[1]Excludes short-term securities.[2]Excludes short-term securities.[3]Excludes short-term securities.[4]Excludes short-term securities.[5]Excludes short-term securities.[6]Excludes short-term securities.[7]Excludes short-term securities.[8]Excludes short-term securities.[9]Excludes short-term securities.[10]Excludes short-term securities.[11]Excludes short-term securities.[12]Excludes short-term securities.[13]Excludes short-term securities.[14]Excludes short-term securities.[15]Excludes short-term securities.[16]Excludes short-term securities.[17]Excludes short-term securities.[18]Excludes short-term securities.[19]Excludes short-term securities.[20]Excludes short-term securities.