| Form N-CSR Cover | 12 Months Ended |
| May 31, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | BlackRock Funds IV |
| Entity Central Index Key | 0001738074 |
| Document Period End Date | May 31, 2024 |
| Shareholder Report | 12 Months Ended |
| May 31, 2024 USD ($) Holding | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | BlackRock Funds IV |
| Entity Central Index Key | 0001738074 |
| Document Period End Date | May 31, 2024 |
| C000202328 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Sustainable Advantage CoreAlpha Bond Fund |
| Class Name | Institutional Shares |
| Trading Symbol | BIIIX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Sustainable Advantage CoreAlpha Bond Fund (the “Fund”) for the period of June 1, 2023 to May 31, 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 $ 0.29 % |
| Expenses Paid, Amount | $ 29 |
| Expense Ratio, Percent | 0.29% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The bond market experienced volatility due to persistent inflation and shifting views regarding the time at which the U.S. Federal Reserve would begin to cut interest rates. Corporate bonds were the best performing segment of the U.S. investment-grade market, while U.S. Treasuries lagged. What contributed to performance? Asset allocation was the primary contributor, mainly due to holdings in securitized assets and an out-of-benchmark position in high yield bonds. Positioning in investment-grade corporates also contributed, led by overweights in the information technology, consumer non-cyclical, and consumer cyclical industries. Relative-value yield curve positioning in the non-U.S. developed markets helped results, as well. The Fund’s cash position had no material impact on performance. What detracted from performance? U.S. Treasury yield curve positioning detracted. The Fund’s allocation to the non-U.S. markets also detracted, primarily due to a global cross-market model that determined long and short positions in 10-year bonds in up to five major markets (the United States, Eurozone, United Kingdom, Canada and Australia). The Fund achieved this positioning through the use of futures. Security selection in mortgage-backed securities was an additional detractor, primarily due to positioning in 15-year conventional and 30-year GNMA securities. 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: August 23, 2016 through May 31, 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 Since Institutional Shares 1.91 % (0.24 ) % 0.55 % Bloomberg U.S. Aggregate Bond Index 1.31 % (0.17 ) % 0.54 % |
| 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 | May 31, 2023 |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 48,415,481 |
| Holdings Count | Holding | 1,452 |
| Advisory Fees Paid, Amount | $ 0 |
| Investment Company Portfolio Turnover | 293% |
| Additional Fund Statistics [Text Block] | Key Fund statistics Net Assets $ % Number of Portfolio Holdings $ % Net Investment Advisory Fees $ % Portfolio Turnover Rate $ % |
| Holdings [Text Block] | What did the Fund invest in? (as of May 31, 2024) Portfolio composition Asset Type Percent of Corporate Bonds 32.8 ) % U.S. Government Sponsored Agency Securities 27.4 ) % U.S. Treasury Obligations 25.7 ) % Non-Agency Mortgage-Backed Securities 9.1 ) % Asset-Backed Securities 5.4 ) % Foreign Agency Obligations 1.2 ) % Municipal Bonds 0.5 ) % Money Market Funds 0.3 ) % TBA Sale Commitments (2.4 ) % Credit quality allocation Credit Rating (a)(b) Percent of AAA/Aaa (c) 48.0 % AA/Aa 3.8 % A 16.5 % BBB/Baa 19.4 % BB/Ba 6.1 % B 2.1 % CCC/Caa 0.3 % N/R 3.8 % (a) (b) (c) For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. (a) (b) (c) Excludes short-term securities. (a) (b) (c) The investment adviser evaluates the credit quality of not-rated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors, individual investments and/or issuer. Using this approach, the investment adviser has deemed U.S. Government Sponsored Agency Securities and U.S. Treasury Obligations as AAA/Aaa. |
| Credit Quality Explanation [Text Block] | The investment adviser evaluates the credit quality of not-rated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors, individual investments and/or issuer. Using this approach, the investment adviser has deemed U.S. Government Sponsored Agency Securities and U.S. Treasury Obligations as AAA/Aaa. |
| Credit Ratings Selection [Text Block] | For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. |
| Material Fund Change [Text Block] | Material Fund changes This is a summary of certain planned changes to the Fund since May 31, 2023. For more complete information, you may review the Fund’s prospectus at blackrock.com/fundreports On June 7, 2024, the Board of Trustees of the Fund approved a proposal to liquidate the Fund. |
| Updated Prospectus Phone Number | (800) 441-7762 |
| Updated Prospectus Web Address | blackrock.com/fundreports |
| C000202330 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Sustainable Advantage CoreAlpha Bond Fund |
| Class Name | Investor A Shares |
| Trading Symbol | BIAAX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Sustainable Advantage CoreAlpha Bond Fund (the “Fund”) for the period of June 1, 2023 to May 31, 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 $ 0.54 % |
| Expenses Paid, Amount | $ 54 |
| Expense Ratio, Percent | 0.54% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The bond market experienced volatility due to persistent inflation and shifting views regarding the time at which the U.S. Federal Reserve would begin to cut interest rates. Corporate bonds were the best performing segment of the U.S. investment-grade market, while U.S. Treasuries lagged. What contributed to performance? Asset allocation was the primary contributor, mainly due to holdings in securitized assets and an out-of-benchmark position in high yield bonds. Positioning in investment-grade corporates also contributed, led by overweights in the information technology, consumer non-cyclical, and consumer cyclical industries. Relative-value yield curve positioning in the non-U.S. developed markets helped results, as well. The Fund’s cash position had no material impact on performance. What detracted from performance? U.S. Treasury yield curve positioning detracted. The Fund’s allocation to the non-U.S. markets also detracted, primarily due to a global cross-market model that determined long and short positions in 10-year bonds in up to five major markets (the United States, Eurozone, United Kingdom, Canada and Australia). The Fund achieved this positioning through the use of futures. Security selection in mortgage-backed securities was an additional detractor, primarily due to positioning in 15-year conventional and 30-year GNMA securities. 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: August 23, 2016 through May 31, 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 Since Investor A Shares 1.66 ) % (0.46 ) % 0.31 ) % Investor A Shares (with sales charge) (2.41 ) % (1.27 ) % (0.22 ) % Bloomberg U.S. Aggregate Bond Index 1.31 ) % (0.17 ) % 0.54 ) % |
| 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 | May 31, 2023 |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 48,415,481 |
| Holdings Count | Holding | 1,452 |
| Advisory Fees Paid, Amount | $ 0 |
| Investment Company Portfolio Turnover | 293% |
| Additional Fund Statistics [Text Block] | Key Fund statistics Net Assets $ % Number of Portfolio Holdings $ % Net Investment Advisory Fees $ % Portfolio Turnover Rate $ % |
| Holdings [Text Block] | What did the Fund invest in? (as of May 31, 2024) Portfolio composition Asset Type Percent of Corporate Bonds 32.8 ) % U.S. Government Sponsored Agency Securities 27.4 ) % U.S. Treasury Obligations 25.7 ) % Non-Agency Mortgage-Backed Securities 9.1 ) % Asset-Backed Securities 5.4 ) % Foreign Agency Obligations 1.2 ) % Municipal Bonds 0.5 ) % Money Market Funds 0.3 ) % TBA Sale Commitments (2.4 ) % Credit quality allocation Credit Rating (a)(b) Percent of AAA/Aaa (c) 48.0 % AA/Aa 3.8 % A 16.5 % BBB/Baa 19.4 % BB/Ba 6.1 % B 2.1 % CCC/Caa 0.3 % N/R 3.8 % (a) (b) (c) For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. (a) (b) (c) Excludes short-term securities. (a) (b) (c) The investment adviser evaluates the credit quality of not-rated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors, individual investments and/or issuer. Using this approach, the investment adviser has deemed U.S. Government Sponsored Agency Securities and U.S. Treasury Obligations as AAA/Aaa. |
| Credit Quality Explanation [Text Block] | The investment adviser evaluates the credit quality of not-rated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors, individual investments and/or issuer. Using this approach, the investment adviser has deemed U.S. Government Sponsored Agency Securities and U.S. Treasury Obligations as AAA/Aaa. |
| Credit Ratings Selection [Text Block] | For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. |
| Material Fund Change [Text Block] | Material Fund changes This is a summary of certain planned changes to the Fund since May 31, 2023. For more complete information, you may review the Fund’s prospectus at blackrock.com/fundreports On June 7, 2024, the Board of Trustees of the Fund approved a proposal to liquidate the Fund. |
| Updated Prospectus Phone Number | (800) 441-7762 |
| Updated Prospectus Web Address | blackrock.com/fundreports |
| C000202329 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Sustainable Advantage CoreAlpha Bond Fund |
| Class Name | Class K Shares |
| Trading Symbol | BIAKX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Sustainable Advantage CoreAlpha Bond Fund (the “Fund”) for the period of June 1, 2023 to May 31, 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 $ 0.24 % |
| Expenses Paid, Amount | $ 24 |
| Expense Ratio, Percent | 0.24% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The bond market experienced volatility due to persistent inflation and shifting views regarding the time at which the U.S. Federal Reserve would begin to cut interest rates. Corporate bonds were the best performing segment of the U.S. investment-grade market, while U.S. Treasuries lagged. What contributed to performance? Asset allocation was the primary contributor, mainly due to holdings in securitized assets and an out-of-benchmark position in high yield bonds. Positioning in investment-grade corporates also contributed, led by overweights in the information technology, consumer non-cyclical, and consumer cyclical industries. Relative-value yield curve positioning in the non-U.S. developed markets helped results, as well. The Fund’s cash position had no material impact on performance. What detracted from performance? U.S. Treasury yield curve positioning detracted. The Fund’s allocation to the non-U.S. markets also detracted, primarily due to a global cross-market model that determined long and short positions in 10-year bonds in up to five major markets (the United States, Eurozone, United Kingdom, Canada and Australia). The Fund achieved this positioning through the use of futures. Security selection in mortgage-backed securities was an additional detractor, primarily due to positioning in 15-year conventional and 30-year GNMA securities. 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: August 23, 2016 through May 31, 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 Since Class K Shares 1.96 % (0.17 ) % 0.61 % Bloomberg U.S. Aggregate Bond Index 1.31 % (0.17 ) % 0.54 % |
| 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 | May 31, 2023 |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 48,415,481 |
| Holdings Count | Holding | 1,452 |
| Advisory Fees Paid, Amount | $ 0 |
| Investment Company Portfolio Turnover | 293% |
| Additional Fund Statistics [Text Block] | Key Fund statistics Net Assets $ % Number of Portfolio Holdings $ % Net Investment Advisory Fees $ % Portfolio Turnover Rate $ % |
| Holdings [Text Block] | What did the Fund invest in? (as of May 31, 2024) Portfolio composition Asset Type Percent of Corporate Bonds 32.8 ) % U.S. Government Sponsored Agency Securities 27.4 ) % U.S. Treasury Obligations 25.7 ) % Non-Agency Mortgage-Backed Securities 9.1 ) % Asset-Backed Securities 5.4 ) % Foreign Agency Obligations 1.2 ) % Municipal Bonds 0.5 ) % Money Market Funds 0.3 ) % TBA Sale Commitments (2.4 ) % Credit quality allocation Credit Rating (a)(b) Percent of AAA/Aaa (c) 48.0 % AA/Aa 3.8 % A 16.5 % BBB/Baa 19.4 % BB/Ba 6.1 % B 2.1 % CCC/Caa 0.3 % N/R 3.8 % (a) (b) (c) For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. (a) (b) (c) Excludes short-term securities. (a) (b) (c) The investment adviser evaluates the credit quality of not-rated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors, individual investments and/or issuer. Using this approach, the investment adviser has deemed U.S. Government Sponsored Agency Securities and U.S. Treasury Obligations as AAA/Aaa. |
| Credit Quality Explanation [Text Block] | The investment adviser evaluates the credit quality of not-rated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors, individual investments and/or issuer. Using this approach, the investment adviser has deemed U.S. Government Sponsored Agency Securities and U.S. Treasury Obligations as AAA/Aaa. |
| Credit Ratings Selection [Text Block] | For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. |
| Material Fund Change [Text Block] | Material Fund changes This is a summary of certain planned changes to the Fund since May 31, 2023. For more complete information, you may review the Fund’s prospectus at blackrock.com/fundreports On June 7, 2024, the Board of Trustees of the Fund approved a proposal to liquidate the Fund. |
| Updated Prospectus Phone Number | (800) 441-7762 |
| Updated Prospectus Web Address | blackrock.com/fundreports |
| C000202331 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Sustainable Advantage CoreAlpha Bond Fund |
| Class Name | Investor C Shares |
| Trading Symbol | BIACX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Sustainable Advantage CoreAlpha Bond Fund (the “Fund”) for the period of June 1, 2023 to May 31, 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 $ 1.29 % |
| Expenses Paid, Amount | $ 130 |
| Expense Ratio, Percent | 1.29% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The bond market experienced volatility due to persistent inflation and shifting views regarding the time at which the U.S. Federal Reserve would begin to cut interest rates. Corporate bonds were the best performing segment of the U.S. investment-grade market, while U.S. Treasuries lagged. What contributed to performance? Asset allocation was the primary contributor, mainly due to holdings in securitized assets and an out-of-benchmark position in high yield bonds. Positioning in investment-grade corporates also contributed, led by overweights in the information technology, consumer non-cyclical, and consumer cyclical industries. Relative-value yield curve positioning in the non-U.S. developed markets helped results, as well. The Fund’s cash position had no material impact on performance. What detracted from performance? U.S. Treasury yield curve positioning detracted. The Fund’s allocation to the non-U.S. markets also detracted, primarily due to a global cross-market model that determined long and short positions in 10-year bonds in up to five major markets (the United States, Eurozone, United Kingdom, Canada and Australia). The Fund achieved this positioning through the use of futures. Security selection in mortgage-backed securities was an additional detractor, primarily due to positioning in 15-year conventional and 30-year GNMA securities. 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: August 23, 2016 through May 31, 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 Since Investor C Shares 0.90 ) % (1.23 ) % (0.46 ) % Investor C Shares (with sales charge) (0.08 ) % (1.23 ) % (0.46 ) % Bloomberg U.S. Aggregate Bond Index 1.31 ) % (0.17 ) % 0.54 ) % |
| 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 | May 31, 2023 |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 48,415,481 |
| Holdings Count | Holding | 1,452 |
| Advisory Fees Paid, Amount | $ 0 |
| Investment Company Portfolio Turnover | 293% |
| Additional Fund Statistics [Text Block] | Key Fund statistics Net Assets $ % Number of Portfolio Holdings $ % Net Investment Advisory Fees $ % Portfolio Turnover Rate $ % |
| Holdings [Text Block] | What did the Fund invest in? (as of May 31, 2024) Portfolio composition Asset Type Percent of Corporate Bonds 32.8 ) % U.S. Government Sponsored Agency Securities 27.4 ) % U.S. Treasury Obligations 25.7 ) % Non-Agency Mortgage-Backed Securities 9.1 ) % Asset-Backed Securities 5.4 ) % Foreign Agency Obligations 1.2 ) % Municipal Bonds 0.5 ) % Money Market Funds 0.3 ) % TBA Sale Commitments (2.4 ) % Credit quality allocation Credit Rating (a)(b) Percent of AAA/Aaa (c) 48.0 % AA/Aa 3.8 % A 16.5 % BBB/Baa 19.4 % BB/Ba 6.1 % B 2.1 % CCC/Caa 0.3 % N/R 3.8 % (a) (b) (c) For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. (a) (b) (c) Excludes short-term securities. (a) (b) (c) The investment adviser evaluates the credit quality of not-rated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors, individual investments and/or issuer. Using this approach, the investment adviser has deemed U.S. Government Sponsored Agency Securities and U.S. Treasury Obligations as AAA/Aaa. |
| Credit Quality Explanation [Text Block] | The investment adviser evaluates the credit quality of not-rated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors, individual investments and/or issuer. Using this approach, the investment adviser has deemed U.S. Government Sponsored Agency Securities and U.S. Treasury Obligations as AAA/Aaa. |
| Credit Ratings Selection [Text Block] | For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. |
| Material Fund Change [Text Block] | Material Fund changes This is a summary of certain planned changes to the Fund since May 31, 2023. For more complete information, you may review the Fund’s prospectus at blackrock.com/fundreports On June 7, 2024, the Board of Trustees of the Fund approved a proposal to liquidate the Fund. |
| Updated Prospectus Phone Number | (800) 441-7762 |
| Updated Prospectus Web Address | blackrock.com/fundreports |
| Shareholder Report, Line Graph (Details) - USD ($) | 12 Months Ended | 60 Months Ended | 93 Months Ended | |||||||
| May 31, 2024 | May 31, 2024 | May 31, 2024 | May 31, 2023 | May 31, 2022 | May 31, 2021 | May 31, 2020 | May 31, 2019 | May 31, 2018 | May 31, 2017 | |
| C000202328 [Member] | ||||||||||
| Account Value [Line Items] | ||||||||||
| Line Graph and Table Measure Name | Institutional Shares | |||||||||
| Account Value | $ 10,435 | $ 10,435 | $ 10,435 | $ 10,239 | $ 10,485 | $ 11,601 | $ 11,610 | $ 10,560 | $ 9,901 | $ 9,968 |
| Average Annual Return, Percent | 1.91% | (0.24%) | 0.55% | |||||||
| C000202330 [Member] | ||||||||||
| Account Value [Line Items] | ||||||||||
| Line Graph and Table Measure Name | Investor A Shares (with sales charge) | |||||||||
| Account Value | $ 9,832 | $ 9,832 | $ 9,832 | 9,671 | 9,917 | 11,000 | 11,036 | 10,064 | 9,459 | 9,550 |
| Average Annual Return, Percent | (2.41%) | (1.27%) | (0.22%) | |||||||
| C000202330 [Member] | Without Sales Load [Member] | ||||||||||
| Account Value [Line Items] | ||||||||||
| Line Graph and Table Measure Name | Investor A Shares | |||||||||
| Average Annual Return, Percent | 1.66% | (0.46%) | 0.31% | |||||||
| C000202329 [Member] | ||||||||||
| Account Value [Line Items] | ||||||||||
| Line Graph and Table Measure Name | Class K Shares | |||||||||
| Account Value | $ 10,482 | $ 10,482 | $ 10,482 | 10,280 | 10,510 | 11,623 | 11,626 | 10,570 | 9,905 | 9,971 |
| Average Annual Return, Percent | 1.96% | (0.17%) | 0.61% | |||||||
| C000202331 [Member] | ||||||||||
| Account Value [Line Items] | ||||||||||
| Line Graph and Table Measure Name | Investor C Shares (with sales charge) | |||||||||
| Account Value | $ 9,651 | $ 9,651 | $ 9,651 | 9,565 | 9,893 | 11,057 | 11,177 | 10,268 | 9,723 | 9,891 |
| Average Annual Return, Percent | (0.08%) | (1.23%) | (0.46%) | |||||||
| C000202331 [Member] | Without Sales Load [Member] | ||||||||||
| Account Value [Line Items] | ||||||||||
| Line Graph and Table Measure Name | Investor C Shares | |||||||||
| Average Annual Return, Percent | 0.90% | (1.23%) | (0.46%) | |||||||
| Bloomberg U S Aggregate Bond Index [Member] | ||||||||||
| Account Value [Line Items] | ||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Aggregate Bond Index | |||||||||
| Account Value | $ 10,428 | $ 10,428 | $ 10,428 | $ 10,294 | $ 10,519 | $ 11,461 | $ 11,508 | $ 10,518 | $ 9,885 | $ 9,922 |
| Average Annual Return, Percent | 1.31% | (0.17%) | 0.54% |
| Shareholder Report, Holdings (Details) | May 31, 2024 | |
| C000202328 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.80% | [1],[2] |
| C000202328 [Member] | U S Treasury Obligations [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 25.70% | |
| C000202328 [Member] | Asset-Backed Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.40% | |
| C000202328 [Member] | TBA Sale Commitments [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | (2.40%) | |
| C000202328 [Member] | Foreign Agency Obligations [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.20% | |
| C000202328 [Member] | Non Agency Mortgage Backed Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.10% | |
| C000202328 [Member] | U S Government Sponsored Agency Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 27.40% | |
| C000202328 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.30% | |
| C000202328 [Member] | Municipal Bonds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.50% | |
| C000202328 [Member] | Corporate Bond Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 32.80% | |
| C000202330 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.80% | [3],[4] |
| C000202330 [Member] | U S Treasury Obligations [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 25.70% | |
| C000202330 [Member] | Asset-Backed Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.40% | |
| C000202330 [Member] | TBA Sale Commitments [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | (2.40%) | |
| C000202330 [Member] | Foreign Agency Obligations [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.20% | |
| C000202330 [Member] | Non Agency Mortgage Backed Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.10% | |
| C000202330 [Member] | U S Government Sponsored Agency Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 27.40% | |
| C000202330 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.30% | |
| C000202330 [Member] | Municipal Bonds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.50% | |
| C000202330 [Member] | Corporate Bond Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 32.80% | |
| C000202329 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.80% | [5],[6] |
| C000202329 [Member] | U S Treasury Obligations [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 25.70% | |
| C000202329 [Member] | Asset-Backed Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.40% | |
| C000202329 [Member] | TBA Sale Commitments [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | (2.40%) | |
| C000202329 [Member] | Foreign Agency Obligations [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.20% | |
| C000202329 [Member] | Non Agency Mortgage Backed Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.10% | |
| C000202329 [Member] | U S Government Sponsored Agency Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 27.40% | |
| C000202329 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.30% | |
| C000202329 [Member] | Municipal Bonds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.50% | |
| C000202329 [Member] | Corporate Bond Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 32.80% | |
| C000202331 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.80% | [7],[8] |
| C000202331 [Member] | U S Treasury Obligations [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 25.70% | |
| C000202331 [Member] | Asset-Backed Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.40% | |
| C000202331 [Member] | TBA Sale Commitments [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | (2.40%) | |
| C000202331 [Member] | Foreign Agency Obligations [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.20% | |
| C000202331 [Member] | Non Agency Mortgage Backed Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.10% | |
| C000202331 [Member] | U S Government Sponsored Agency Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 27.40% | |
| C000202331 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.30% | |
| C000202331 [Member] | Municipal Bonds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.50% | |
| C000202331 [Member] | Corporate Bond Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 32.80% | |
| [1]Excludes short-term securities.[2]For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.[3]Excludes short-term securities.[4]For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.[5]Excludes short-term securities.[6]For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.[7]Excludes short-term securities.[8]For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. | ||
| Label | Element | Value | |
| C000202331 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 19.40% | [1],[2] |
| C000202331 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 48% | [1],[2],[3] |
| C000202331 [Member] | Standard & Poor's, B Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 2.10% | [1],[2] |
| C000202331 [Member] | Standard & Poor's, CCC Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 0.30% | [1],[2] |
| C000202331 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 3.80% | [1],[2] |
| C000202331 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 16.50% | [1],[2] |
| C000202331 [Member] | Standard & Poor's, BB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 6.10% | [1],[2] |
| C000202328 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 19.40% | [4],[5] |
| C000202328 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 48% | [4],[5],[6] |
| C000202328 [Member] | Standard & Poor's, B Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 2.10% | [4],[5] |
| C000202328 [Member] | Standard & Poor's, CCC Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 0.30% | [4],[5] |
| C000202328 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 3.80% | [4],[5] |
| C000202328 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 16.50% | [4],[5] |
| C000202328 [Member] | Standard & Poor's, BB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 6.10% | [4],[5] |
| C000202330 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 19.40% | [7],[8] |
| C000202330 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 48% | [7],[8],[9] |
| C000202330 [Member] | Standard & Poor's, B Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 2.10% | [7],[8] |
| C000202330 [Member] | Standard & Poor's, CCC Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 0.30% | [7],[8] |
| C000202330 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 3.80% | [7],[8] |
| C000202330 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 16.50% | [7],[8] |
| C000202330 [Member] | Standard & Poor's, BB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 6.10% | [7],[8] |
| C000202329 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 19.40% | [10],[11] |
| C000202329 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 48% | [10],[11],[12] |
| C000202329 [Member] | Standard & Poor's, B Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 2.10% | [10],[11] |
| C000202329 [Member] | Standard & Poor's, CCC Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 0.30% | [10],[11] |
| C000202329 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 3.80% | [10],[11] |
| C000202329 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 16.50% | [10],[11] |
| C000202329 [Member] | Standard & Poor's, BB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 6.10% | [10],[11] |
| [1]Excludes short-term securities.[2]For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.[3]The investment adviser evaluates the credit quality of not-rated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors, individual investments and/or issuer. Using this approach, the investment adviser has deemed U.S. Government Sponsored Agency Securities and U.S. Treasury Obligations as AAA/Aaa.[4]Excludes short-term securities.[5]For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.[6]The investment adviser evaluates the credit quality of not-rated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors, individual investments and/or issuer. Using this approach, the investment adviser has deemed U.S. Government Sponsored Agency Securities and U.S. Treasury Obligations as AAA/Aaa.[7]Excludes short-term securities.[8]For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.[9]The investment adviser evaluates the credit quality of not-rated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors, individual investments and/or issuer. Using this approach, the investment adviser has deemed U.S. Government Sponsored Agency Securities and U.S. Treasury Obligations as AAA/Aaa.[10]Excludes short-term securities.[11]For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.[12]The investment adviser evaluates the credit quality of not-rated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors, individual investments and/or issuer. Using this approach, the investment adviser has deemed U.S. Government Sponsored Agency Securities and U.S. Treasury Obligations as AAA/Aaa. | |||
