| Shareholder Report | 12 Months Ended |
| Dec. 31, 2024 USD ($) Holding |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | BlackRock Series Fund, Inc. |
| Entity Central Index Key | 0000319108 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Dec. 31, 2024 |
| C000010830 | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Advantage Large Cap Core Portfolio |
| Trading Symbol | LGCCS |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Advantage Large Cap Core Portfolio (the “Fund”) for the period of January 1, 2024 to December 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] | |
| 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) Fund name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment BlackRock Advantage Large Cap Core Portfolio $55 0.49% |
| Expenses Paid, Amount | $ 55 |
| Expense Ratio, Percent | 0.49% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? For the reporting period ended December 31, 2024, the Fund's Class I Shares returned 25.61%. For the same period, the Russell 1000 ® What contributed to performance? The Fund delivered strong performance during the reporting period, driven primarily by sentiment- and macro-related insights. Tracking social media activity helped correctly position the portfolio in the consumer discretionary sector, contributing to absolute performance. Furthermore, measures that gather sentiment from informed investor positioning worked well in healthcare. Positioning in the sector was also driven by a macro-related insight favoring companies likely to benefit from growing demand for GLP-1 treatments. Macro-related insights that assess industry-level positioning, which led to holdings in information technology stocks that benefited from enthusiasm about artificial intelligence, further helped results. What detracted from performance? Given the Fund’s strong performance, there were no major detractors from absolute returns. However, certain fundamental measures struggled. Traditional valuation measures looking at company cash flow levels incorrectly positioned the portfolio in metals and mining companies that posted negative returns. Additionally, quality insights with a preference for more stable companies lagged due to the “risk-off” tone in the market. |
| Performance Past Does Not Indicate Future [Text] | Past performance is not an indication of future results. |
| Line Graph [Table Text Block] | BlackRock Advantage Large Cap Core Portfolio Russell 1000 ® Jan 15 $9,506 $9,725 Feb 15 $10,167 $10,287 Mar 15 $10,021 $10,159 Apr 15 $10,036 $10,231 May 15 $10,235 $10,365 Jun 15 $10,075 $10,171 Jul 15 $10,311 $10,367 Aug 15 $9,694 $9,743 Sep 15 $9,404 $9,476 Oct 15 $10,186 $10,243 Nov 15 $10,189 $10,277 Dec 15 $10,060 $10,092 Jan 16 $9,378 $9,549 Feb 16 $9,260 $9,545 Mar 16 $9,893 $10,210 Apr 16 $9,829 $10,266 May 16 $9,996 $10,446 Jun 16 $9,863 $10,469 Jul 16 $10,258 $10,868 Aug 16 $10,365 $10,882 Sep 16 $10,377 $10,891 Oct 16 $10,266 $10,679 Nov 16 $10,898 $11,100 Dec 16 $11,135 $11,308 Jan 17 $11,381 $11,536 Feb 17 $11,902 $11,982 Mar 17 $11,873 $11,990 Apr 17 $12,082 $12,116 May 17 $12,156 $12,271 Jun 17 $12,197 $12,357 Jul 17 $12,444 $12,601 Aug 17 $12,532 $12,641 Sep 17 $12,861 $12,910 Oct 17 $13,131 $13,206 Nov 17 $13,506 $13,609 Dec 17 $13,611 $13,761 Jan 18 $14,513 $14,516 Feb 18 $14,059 $13,983 Mar 18 $13,807 $13,666 Apr 18 $13,774 $13,712 May 18 $14,070 $14,062 Jun 18 $14,115 $14,153 Jul 18 $14,584 $14,642 Aug 18 $15,119 $15,146 Sep 18 $15,154 $15,204 Oct 18 $13,980 $14,128 Nov 18 $14,202 $14,415 Dec 18 $12,915 $13,102 Jan 19 $14,046 $14,200 Feb 19 $14,549 $14,681 Mar 19 $14,713 $14,937 Apr 19 $15,321 $15,540 May 19 $14,464 $14,550 Jun 19 $15,314 $15,571 Jul 19 $15,482 $15,813 Aug 19 $15,142 $15,523 Sep 19 $15,364 $15,792 Oct 19 $15,672 $16,127 Nov 19 $16,240 $16,736 Dec 19 $16,673 $17,220 Jan 20 $16,770 $17,238 Feb 20 $15,396 $15,830 Mar 20 $13,387 $13,738 Apr 20 $15,187 $15,553 May 20 $15,940 $16,374 Jun 20 $16,317 $16,736 Jul 20 $17,196 $17,716 Aug 20 $18,530 $19,016 Sep 20 $17,803 $18,321 Oct 20 $17,224 $17,879 Nov 20 $19,229 $19,985 Dec 20 $20,006 $20,830 Jan 21 $19,822 $20,658 Feb 21 $20,465 $21,257 Mar 21 $21,276 $22,061 Apr 21 $22,432 $23,249 May 21 $22,677 $23,359 Jun 21 $23,190 $23,944 Jul 21 $23,794 $24,442 Aug 21 $24,350 $25,149 Sep 21 $23,176 $23,994 Oct 21 $24,734 $25,659 Nov 21 $24,624 $25,315 Dec 21 $25,694 $26,340 Jan 22 $24,232 $24,855 Feb 22 $23,393 $24,173 Mar 22 $24,138 $24,989 Apr 22 $22,053 $22,761 May 22 $22,025 $22,727 Jun 22 $20,167 $20,823 Jul 22 $21,825 $22,763 Aug 22 $20,929 $21,889 Sep 22 $19,059 $19,863 Oct 22 $20,686 $21,456 Nov 22 $21,815 $22,617 Dec 22 $20,583 $21,302 Jan 23 $21,906 $22,730 Feb 23 $21,412 $22,189 Mar 23 $22,054 $22,891 Apr 23 $22,212 $23,175 May 23 $22,202 $23,283 Jun 23 $23,800 $24,855 Jul 23 $24,511 $25,710 Aug 23 $24,165 $25,260 Sep 23 $23,050 $24,073 Oct 23 $22,567 $23,491 Nov 23 $24,688 $25,685 Dec 23 $25,813 $26,953 Jan 24 $26,259 $27,329 Feb 24 $27,547 $28,805 Mar 24 $28,814 $29,728 Apr 24 $27,607 $28,463 May 24 $29,037 $29,804 Jun 24 $30,091 $30,790 Jul 24 $30,501 $31,238 Aug 24 $31,238 $31,979 Sep 24 $31,842 $32,663 Oct 24 $31,504 $32,434 Nov 24 $33,356 $34,522 Dec 24 $32,424 $33,560 |
| Average Annual Return [Table Text Block] | Average Annual Total Returns 1 Year 5 years 10 Years BlackRock Advantage Large Cap Core Portfolio ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 25.61 % 14.23 % 12.48 % Russell 1000 ® ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 24.51 14.28 12.87 |
| 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. |
| Performance Table Market Index Changed [Text Block] | |
| Material Change Description [Text Block] | |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| AssetsNet | $ 214,130,833 |
| Holdings Count | Holding | 193 |
| Advisory Fees Paid, Amount | $ 770,908 |
| InvestmentCompanyPortfolioTurnover | 115% |
| Additional Fund Statistics [Text Block] | Key Fund statistics Net Assets ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ $214,130,833 Number of Portfolio Holdings ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 193 Net Investment Advisory Fees ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ $770,908 Portfolio Turnover Rate ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 115% |
| Holdings [Text Block] | Sector allocation Sector Footnote Reference (a) Percent of
Net Assets Information Technology ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 30.9 % Financials ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 14.2 Consumer Discretionary ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 11.7 Industrials ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 10.3 Health Care ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 10.2 Communication Services ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 9.4 Consumer Staples ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 4.3 Materials ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 2.6 Energy ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 2.4 Real Estate ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 1.8 Utilities ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 1.3 Short-Term Securities ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 3.2 Liabilities in Excess of Other Assets ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ (2.3 ) Footnote Description Footnote (a) For purpose of this report, sector sub-classifications may differ from those utilized by the Fund for compliance purposes. |
| C000010833 | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Capital Appreciation Portfolio |
| Trading Symbol | FDGRS |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Capital Appreciation Portfolio (the “Fund”) for the period of January 1, 2024 to December 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] | |
| 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) Fund name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment BlackRock Capital Appreciation Portfolio $55 0.47% |
| Expenses Paid, Amount | $ 55 |
| Expense Ratio, Percent | 0.47% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? For the reporting period ended December 31, 2024, the Fund's Class I Shares returned 31.51%. For the same period, the S&P 500 ® ® What contributed to performance? Positive contributions to the Fund’s performance over the reporting period were led by positioning in the information technology, communication services and consumer discretionary sectors. In information technology, holdings in the semiconductors and semiconductor equipment industry proved beneficial, most notably exposure to a provider of chips used in artificial intelligence applications. In communication services, positioning in interactive media and services was most additive, led by exposure to a social media platform operator. Finally, in consumer discretionary, positioning in the broadline retail industry contributed, most notably holdings of an online retail platform operator. What detracted from performance? The largest detractors from performance over the period were investment decisions in the real estate and energy sectors. In real estate, positioning in the management and development industry detracted, in particular exposure to a provider of real estate industry analytics. In energy, positioning in oil, gas, and consumable fuels weighed on return, most notably holdings of an exporter of liquified natural gas. While no other sector detracted from absolute performance, in information technology services holdings of a developer data platform provider was among the Fund’s largest individual detractors. |
| Performance Past Does Not Indicate Future [Text] | Past performance is not an indication of future results. |
| Line Graph [Table Text Block] | BlackRock Capital Appreciation Portfolio S&P 500 ® Russell 1000 ® Jan 15 $9,830 $9,700 $9,847 Feb 15 $10,499 $10,257 $10,503 Mar 15 $10,401 $10,095 $10,384 Apr 15 $10,519 $10,192 $10,436 May 15 $10,735 $10,323 $10,583 Jun 15 $10,640 $10,123 $10,396 Jul 15 $11,121 $10,335 $10,749 Aug 15 $10,374 $9,712 $10,096 Sep 15 $9,917 $9,471 $9,846 Oct 15 $10,767 $10,270 $10,694 Nov 15 $10,896 $10,301 $10,724 Dec 15 $10,727 $10,138 $10,567 Jan 16 $9,886 $9,635 $9,977 Feb 16 $9,655 $9,622 $9,973 Mar 16 $10,189 $10,275 $10,645 Apr 16 $10,114 $10,315 $10,548 May 16 $10,470 $10,500 $10,753 Jun 16 $10,280 $10,527 $10,711 Jul 16 $10,849 $10,915 $11,216 Aug 16 $10,906 $10,931 $11,160 Sep 16 $11,087 $10,933 $11,201 Oct 16 $10,814 $10,733 $10,938 Nov 16 $10,693 $11,131 $11,176 Dec 16 $10,769 $11,351 $11,314 Jan 17 $11,250 $11,566 $11,696 Feb 17 $11,727 $12,025 $12,182 Mar 17 $11,865 $12,039 $12,322 Apr 17 $12,230 $12,163 $12,604 May 17 $12,583 $12,334 $12,932 Jun 17 $12,666 $12,411 $12,898 Jul 17 $13,228 $12,666 $13,241 Aug 17 $13,343 $12,705 $13,483 Sep 17 $13,363 $12,967 $13,659 Oct 17 $14,020 $13,270 $14,188 Nov 17 $14,306 $13,677 $14,619 Dec 17 $14,394 $13,829 $14,733 Jan 18 $15,894 $14,621 $15,776 Feb 18 $15,582 $14,082 $15,363 Mar 18 $15,238 $13,724 $14,941 Apr 18 $15,536 $13,777 $14,994 May 18 $16,182 $14,108 $15,651 Jun 18 $16,522 $14,195 $15,801 Jul 18 $16,712 $14,724 $16,265 Aug 18 $17,403 $15,203 $17,155 Sep 18 $17,486 $15,290 $17,251 Oct 18 $15,646 $14,245 $15,708 Nov 18 $16,089 $14,535 $15,875 Dec 18 $14,738 $13,223 $14,510 Jan 19 $16,211 $14,282 $15,814 Feb 19 $16,766 $14,741 $16,380 Mar 19 $17,265 $15,027 $16,846 Apr 19 $18,025 $15,636 $17,607 May 19 $17,160 $14,642 $16,495 Jun 19 $18,295 $15,674 $17,628 Jul 19 $18,385 $15,899 $18,026 Aug 19 $18,251 $15,648 $17,888 Sep 19 $17,855 $15,940 $17,890 Oct 19 $18,170 $16,286 $18,394 Nov 19 $19,122 $16,877 $19,210 Dec 19 $19,570 $17,386 $19,790 Jan 20 $20,269 $17,379 $20,232 Feb 20 $19,209 $15,949 $18,854 Mar 20 $17,256 $13,979 $17,000 Apr 20 $19,823 $15,771 $19,515 May 20 $21,406 $16,522 $20,825 Jun 20 $22,267 $16,850 $21,732 Jul 20 $23,563 $17,801 $23,404 Aug 20 $25,636 $19,080 $25,819 Sep 20 $24,732 $18,355 $24,604 Oct 20 $23,982 $17,867 $23,769 Nov 20 $26,400 $19,823 $26,203 Dec 20 $27,430 $20,585 $27,408 Jan 21 $27,065 $20,377 $27,205 Feb 21 $27,469 $20,939 $27,199 Mar 21 $27,547 $21,856 $27,666 Apr 21 $29,627 $23,022 $29,548 May 21 $29,252 $23,183 $29,140 Jun 21 $31,133 $23,724 $30,968 Jul 21 $32,204 $24,288 $31,988 Aug 21 $33,258 $25,026 $33,184 Sep 21 $31,336 $23,863 $31,326 Oct 21 $33,347 $25,534 $34,039 Nov 21 $32,888 $25,357 $34,247 Dec 21 $33,250 $26,494 $34,971 Jan 22 $29,517 $25,123 $31,970 Feb 22 $28,046 $24,371 $30,612 Mar 22 $28,744 $25,276 $31,809 Apr 22 $24,779 $23,071 $27,968 May 22 $24,256 $23,114 $27,318 Jun 22 $22,104 $21,206 $25,154 Jul 22 $24,863 $23,161 $28,173 Aug 22 $23,043 $22,217 $26,861 Sep 22 $20,508 $20,170 $24,249 Oct 22 $21,333 $21,804 $25,667 Nov 22 $22,588 $23,022 $26,836 Dec 22 $20,752 $21,696 $24,782 Jan 23 $23,034 $23,059 $26,847 Feb 23 $22,504 $22,496 $26,528 Mar 23 $24,262 $23,322 $28,342 Apr 23 $24,598 $23,686 $28,621 May 23 $25,949 $23,789 $29,926 Jun 23 $27,797 $25,361 $31,972 Jul 23 $28,561 $26,176 $33,050 Aug 23 $28,600 $25,759 $32,753 Sep 23 $26,776 $24,531 $30,972 Oct 23 $26,421 $24,015 $30,531 Nov 23 $29,745 $26,208 $33,859 Dec 23 $31,046 $27,399 $35,358 Jan 24 $32,260 $27,859 $36,240 Feb 24 $34,587 $29,347 $38,713 Mar 24 $35,257 $30,291 $39,394 Apr 24 $33,553 $29,054 $37,723 May 24 $35,502 $30,494 $39,981 Jun 24 $37,876 $31,589 $42,677 Jul 24 $36,879 $31,973 $41,951 Aug 24 $37,787 $32,749 $42,825 Sep 24 $38,488 $33,448 $44,038 Oct 24 $38,187 $33,145 $43,893 Nov 24 $40,577 $35,090 $46,740 Dec 24 $40,830 $34,254 $47,152 |
| Average Annual Return [Table Text Block] | Average Annual Total Returns 1 Year 5 years 10 Years BlackRock Capital Appreciation Portfolio ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 31.51 % 15.85 % 15.11 % S&P 500 ® ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 25.02 14.53 13.10 Russell 1000 ® ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 33.36 18.96 16.78 |
| 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. |
| Performance Table Market Index Changed [Text Block] | |
| Material Change Description [Text Block] | |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| AssetsNet | $ 255,120,973 |
| Holdings Count | Holding | 38 |
| Advisory Fees Paid, Amount | $ 896,603 |
| InvestmentCompanyPortfolioTurnover | 27% |
| Additional Fund Statistics [Text Block] | Key Fund statistics Net Assets ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ $255,120,973 Number of Portfolio Holdings ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 38 Net Investment Advisory Fees ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ $896,603 Portfolio Turnover Rate ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 27% |
| Holdings [Text Block] | Sector allocation Sector Footnote Reference (a) Percent of
Net Assets Information Technology ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 47.0 % Consumer Discretionary ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 14.9 Communication Services ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 14.1 Health Care ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 8.3 Financials ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 7.4 Industrials ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 6.0 Materials ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 1.3 Real Estate ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 1.0 Short-Term Securities ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 0.1 Liabilities in Excess of Other Assets ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ (0.1 ) Footnote Description Footnote (a) For purpose of this report, sector sub-classifications may differ from those utilized by the Fund for compliance purposes. |
| C000010832 | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Global Allocation Portfolio |
| Trading Symbol | GLALS |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Global Allocation Portfolio (the “Fund”) for the period of January 1, 2024 to December 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] | |
| 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) Fund name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment BlackRock Global Allocation Portfolio $60 0.57% |
| Expenses Paid, Amount | $ 60 |
| Expense Ratio, Percent | 0.57% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? For the reporting period ended December 31, 2024, the Fund's Class I Shares returned 9.74%. For the same period, the FTSE World Index returned 17.96% and the Reference Benchmark returned 9.09%. What contributed to performance? The Fund’s positive absolute return was primarily driven by equity positioning. Within equities, positioning in information technology and financials as well as, to a lesser extent, consumer discretionary and communication services were the primary contributors to absolute return. Within fixed income, positioning in high yield corporate bonds and securitized assets, notably commercial mortgage-backed securities and asset-backed securities, positively impacted return, as did positioning in nominal U.S. Treasuries. The Fund’s exposure to cash and cash equivalents was actively managed over the period and used to help mitigate portfolio volatility while serving as a source of funds for new investments and to meet redemptions. The Fund’s cash exposure had a slight positive impact on absolute return. What detracted from performance? Within equities, positioning in index-related equity futures used mainly as a hedge during periods of heightened market volatility was the primary detractor from absolute return. Within fixed income, management of duration (interest rate sensitivity) via interest rate derivatives negatively impacted absolute performance along with exposure to agency mortgage-backed securities and U.K. interest rates. |
| Performance Past Does Not Indicate Future [Text] | Past performance is not an indication of future results. |
| Line Graph [Table Text Block] | BlackRock Global Allocation Portfolio FTSE World Index Reference Benchmark Jan 15 $10,013 $9,835 $9,919 Feb 15 $10,354 $10,390 $10,207 Mar 15 $10,284 $10,231 $10,097 Apr 15 $10,477 $10,503 $10,271 May 15 $10,509 $10,515 $10,235 Jun 15 $10,316 $10,280 $10,087 Jul 15 $10,313 $10,411 $10,193 Aug 15 $9,947 $9,722 $9,808 Sep 15 $9,665 $9,367 $9,644 Oct 15 $10,078 $10,106 $10,100 Nov 15 $10,032 $10,041 $10,007 Dec 15 $9,938 $9,863 $9,922 Jan 16 $9,603 $9,282 $9,655 Feb 16 $9,498 $9,227 $9,698 Mar 16 $9,896 $9,906 $10,185 Apr 16 $10,015 $10,061 $10,296 May 16 $9,966 $10,090 $10,280 Jun 16 $9,966 $10,015 $10,360 Jul 16 $10,252 $10,452 $10,636 Aug 16 $10,301 $10,472 $10,613 Sep 16 $10,356 $10,538 $10,671 Oct 16 $10,224 $10,363 $10,469 Nov 16 $10,259 $10,464 $10,394 Dec 16 $10,360 $10,716 $10,523 Jan 17 $10,551 $11,000 $10,710 Feb 17 $10,743 $11,317 $10,916 Mar 17 $10,835 $11,454 $10,990 Apr 17 $10,970 $11,639 $11,138 May 17 $11,147 $11,902 $11,337 Jun 17 $11,169 $11,958 $11,356 Jul 17 $11,401 $12,265 $11,588 Aug 17 $11,444 $12,306 $11,651 Sep 17 $11,515 $12,563 $11,747 Oct 17 $11,607 $12,817 $11,874 Nov 17 $11,743 $13,084 $12,063 Dec 17 $11,816 $13,296 $12,175 Jan 18 $12,247 $14,015 $12,596 Feb 18 $11,873 $13,450 $12,268 Mar 18 $11,772 $13,177 $12,168 Apr 18 $11,722 $13,317 $12,169 May 18 $11,715 $13,335 $12,178 Jun 18 $11,643 $13,290 $12,148 Jul 18 $11,864 $13,715 $12,374 Aug 18 $11,886 $13,846 $12,469 Sep 18 $11,835 $13,940 $12,480 Oct 18 $11,285 $12,911 $11,905 Nov 18 $11,424 $13,067 $12,026 Dec 18 $10,957 $12,131 $11,606 Jan 19 $11,528 $13,078 $12,198 Feb 19 $11,667 $13,436 $12,367 Mar 19 $11,790 $13,598 $12,524 Apr 19 $11,983 $14,077 $12,777 May 19 $11,667 $13,275 $12,421 Jun 19 $12,145 $14,149 $13,008 Jul 19 $12,103 $14,205 $13,017 Aug 19 $12,111 $13,892 $12,972 Sep 19 $12,204 $14,218 $13,101 Oct 19 $12,469 $14,609 $13,340 Nov 19 $12,640 $14,984 $13,495 Dec 19 $12,943 $15,496 $13,787 Jan 20 $12,967 $15,352 $13,785 Feb 20 $12,451 $14,060 $13,154 Mar 20 $11,337 $12,163 $12,128 Apr 20 $12,265 $13,483 $12,941 May 20 $12,741 $14,128 $13,310 Jun 20 $12,999 $14,536 $13,557 Jul 20 $13,676 $15,256 $14,072 Aug 20 $14,215 $16,225 $14,574 Sep 20 $13,995 $15,698 $14,286 Oct 20 $13,733 $15,232 $14,023 Nov 20 $15,032 $17,217 $15,149 Dec 20 $15,644 $18,027 $15,626 Jan 21 $15,566 $17,877 $15,497 Feb 21 $15,775 $18,323 $15,618 Mar 21 $15,905 $18,938 $15,870 Apr 21 $16,463 $19,814 $16,360 May 21 $16,689 $20,125 $16,580 Jun 21 $16,680 $20,391 $16,621 Jul 21 $16,680 $20,678 $16,850 Aug 21 $16,848 $21,187 $17,072 Sep 21 $16,310 $20,301 $16,534 Oct 21 $16,769 $21,363 $16,987 Nov 21 $16,310 $20,870 $16,763 Dec 21 $16,706 $21,804 $17,210 Jan 22 $16,042 $20,707 $16,593 Feb 22 $15,685 $20,222 $16,315 Mar 22 $15,556 $20,769 $16,367 Apr 22 $14,703 $19,060 $15,301 May 22 $14,842 $19,124 $15,374 Jun 22 $13,940 $17,419 $14,399 Jul 22 $14,583 $18,740 $15,144 Aug 22 $14,149 $18,003 $14,546 Sep 22 $13,203 $16,302 $13,463 Oct 22 $13,666 $17,434 $14,006 Nov 22 $14,462 $18,728 $14,870 Dec 22 $14,079 $17,979 $14,526 Jan 23 $14,817 $19,269 $15,290 Feb 23 $14,304 $18,787 $14,870 Mar 23 $14,632 $19,368 $15,356 Apr 23 $14,755 $19,701 $15,560 May 23 $14,612 $19,548 $15,355 Jun 23 $15,104 $20,689 $15,851 Jul 23 $15,390 $21,405 $16,194 Aug 23 $15,042 $20,872 $15,889 Sep 23 $14,499 $19,997 $15,339 Oct 23 $14,294 $19,417 $15,026 Nov 23 $15,257 $21,271 $16,114 Dec 23 $15,934 $22,326 $16,806 Jan 24 $15,944 $22,530 $16,835 Feb 24 $16,387 $23,469 $17,145 Mar 24 $16,809 $24,240 $17,523 Apr 24 $16,197 $23,369 $17,000 May 24 $16,767 $24,374 $17,513 Jun 24 $16,967 $24,906 $17,735 Jul 24 $17,155 $25,346 $18,117 Aug 24 $17,532 $26,028 $18,545 Sep 24 $17,822 $26,496 $18,848 Oct 24 $17,392 $25,946 $18,341 Nov 24 $17,919 $27,001 $18,731 Dec 24 $17,486 $26,336 $18,334 |
| Average Annual Return [Table Text Block] | Average Annual Total Returns 1 Year 5 years 10 Years BlackRock Global Allocation Portfolio ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 9.74 % 6.20 % 5.75 % FTSE World Index ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 17.96 11.19 10.17 Reference Benchmark ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 9.09 5.87 6.25 |
| 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. |
| Performance Table Market Index Changed [Text Block] | |
| Material Change Description [Text Block] | |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| AssetsNet | $ 146,008,958 |
| Holdings Count | Holding | 1,674 |
| Advisory Fees Paid, Amount | $ 132,200 |
| InvestmentCompanyPortfolioTurnover | 155% |
| Additional Fund Statistics [Text Block] | Key Fund statistics Net Assets ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ $146,008,958 Number of Portfolio Holdings ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 1,674 Net Investment Advisory Fees ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ $132,200 Portfolio Turnover Rate ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 155% |
| Holdings [Text Block] | Geographic allocation Percent of Total
Investments Footnote Reference (a) Country/Geographic Region Long Short Total United States ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 66.5 % - % 66.5 % United Kingdom ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 4.8 - 4.8 Japan ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 3.5 - 3.5 France ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 3.3 - 3.3 Italy ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 2.3 - 2.3 Netherlands ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 2.3 - 2.3 Canada ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 1.8 - 1.8 China ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 1.7 - 1.7 Germany ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 1.7 - 1.7 Taiwan ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 1.3 - 1.3 Other Footnote Reference (b) ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 10.8 - 10.8 Total ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 100.0 % - % 100.0 % Footnote Description Footnote (a) Includes the gross market value of long and short securities and excludes short-term securities and options, if any. Footnote (b) Ten largest countries/geographic regions are presented. Additional countries/geographic regions are found in Other. |
| C000010836 | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Government Money Market Portfolio |
| Trading Symbol | MNRSV |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Government Money Market Portfolio (the “Fund”) for the period of January 1, 2024 to December 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 |
| 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) Fund name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment BlackRock Government Money Market Portfolio $51 0.50% |
| Expenses Paid, Amount | $ 51 |
| Expense Ratio, Percent | 0.50% |
| AssetsNet | $ 108,096,016 |
| Holdings Count | Holding | 88 |
| Advisory Fees Paid, Amount | $ 415,291 |
| Additional Fund Statistics [Text Block] | Key Fund statistics Net Assets ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ $108,096,016 Number of Portfolio Holdings ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 88 Net Investment Advisory Fees ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ $415,291 Current seven-day yields as of December 31, 2024 (The 7-day SEC Yield may differ from the 7-Day Yield shown due to the fact that the 7-Day SEC Yield excludes distributed capital gains.) 0 7-Day SEC Yield ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 4.09% 7-Day Yield ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 4.09% |
| Holdings [Text Block] | Portfolio composition Asset Type Percent of
Net Assets Repurchase Agreements ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 39.5 % U.S. Treasury Obligations ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 39.2 U.S. Government Sponsored Agency Obligations ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 17.7 Other Assets Less Liabilities ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 3.6 |
| C000010829 | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Sustainable Balanced Portfolio |
| Trading Symbol | BLCPS |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Sustainable Balanced Portfolio (the “Fund”) for the period of January 1, 2024 to December 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] | |
| 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) Fund name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment BlackRock Sustainable Balanced Portfolio $51 0.48% |
| Expenses Paid, Amount | $ 51 |
| Expense Ratio, Percent | 0.48% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? For the reporting period ended December 31, 2024, the Fund's Class I Shares returned 12.88%. For the same period, the MSCI All Country World Index returned 17.49% and the Bloomberg U.S. Aggregate Bond Index returned 1.25%. What contributed to performance? The portfolio has three main drivers of absolute performance: tactical asset allocation (including stock, bond, and currency positioning, as well as regional tilts), equity security selection, and fixed income security selection. Given the positive returns for global equities and U.S. bonds in 2024, all three strategies made positive contributions to absolute returns. The Fund held derivatives as a part of its investment strategy. The portfolio management team used derivatives as a means to manage risk and/or take outright views on equities and bonds. Derivatives held to express active asset allocation views produced positive returns in the annual period. What detracted from performance? Currency positioning in tactical asset allocation strategy detracted. The Fund was positioned short in the U.S. dollar versus a basket of developed market currencies, which was a negative at a time of dollar strength. With respect to security selection in equities, environmental, social, and governance-related insights detracted. Fundamental valuation measures also experienced negative absolute returns given the market’s focus on a very narrow group of richly valued U.S. technology stocks. |
| Performance Past Does Not Indicate Future [Text] | Past performance is not an indication of future results. |
| Line Graph [Table Text Block] | BlackRock Sustainable Balanced Portfolio MSCI All Country World Index Bloomberg U.S. Aggregate Bond Index 60% MSCI All Country World Index / 40% Bloomberg U.S. Aggregate Bond Index Jan 15 $9,736 $9,844 $10,210 $9,990 Feb 15 $10,163 $10,392 $10,114 $10,286 Mar 15 $10,090 $10,231 $10,161 $10,210 Apr 15 $10,090 $10,528 $10,124 $10,373 May 15 $10,202 $10,514 $10,100 $10,355 Jun 15 $10,056 $10,266 $9,990 $10,163 Jul 15 $10,226 $10,355 $10,059 $10,244 Aug 15 $9,841 $9,646 $10,045 $9,817 Sep 15 $9,677 $9,296 $10,113 $9,630 Oct 15 $10,163 $10,026 $10,114 $10,084 Nov 15 $10,152 $9,943 $10,088 $10,024 Dec 15 $10,052 $9,764 $10,055 $9,902 Jan 16 $9,680 $9,175 $10,193 $9,599 Feb 16 $9,668 $9,112 $10,266 $9,586 Mar 16 $10,118 $9,787 $10,360 $10,048 Apr 16 $10,100 $9,931 $10,400 $10,152 May 16 $10,203 $9,944 $10,402 $10,161 Jun 16 $10,197 $9,884 $10,589 $10,197 Jul 16 $10,471 $10,310 $10,656 $10,486 Aug 16 $10,531 $10,344 $10,644 $10,503 Sep 16 $10,550 $10,408 $10,638 $10,539 Oct 16 $10,459 $10,231 $10,556 $10,399 Nov 16 $10,773 $10,309 $10,307 $10,348 Dec 16 $10,922 $10,531 $10,321 $10,488 Jan 17 $11,077 $10,819 $10,341 $10,669 Feb 17 $11,414 $11,123 $10,411 $10,877 Mar 17 $11,401 $11,259 $10,405 $10,954 Apr 17 $11,569 $11,434 $10,486 $11,091 May 17 $11,653 $11,687 $10,567 $11,272 Jun 17 $11,679 $11,740 $10,556 $11,298 Jul 17 $11,831 $12,068 $10,601 $11,507 Aug 17 $11,917 $12,114 $10,696 $11,575 Sep 17 $12,108 $12,348 $10,645 $11,687 Oct 17 $12,272 $12,605 $10,652 $11,835 Nov 17 $12,463 $12,849 $10,638 $11,966 Dec 17 $12,515 $13,056 $10,687 $12,104 Jan 18 $12,982 $13,793 $10,564 $12,458 Feb 18 $12,729 $13,213 $10,464 $12,097 Mar 18 $12,594 $12,931 $10,531 $11,973 Apr 18 $12,594 $13,054 $10,452 $12,006 May 18 $12,768 $13,070 $10,527 $12,049 Jun 18 $12,784 $13,000 $10,514 $12,004 Jul 18 $13,047 $13,392 $10,516 $12,222 Aug 18 $13,344 $13,497 $10,584 $12,311 Sep 18 $13,368 $13,555 $10,516 $12,312 Oct 18 $12,678 $12,540 $10,433 $11,719 Nov 18 $12,838 $12,723 $10,495 $11,850 Dec 18 $12,182 $11,827 $10,688 $11,436 Jan 19 $12,950 $12,761 $10,801 $12,027 Feb 19 $13,220 $13,102 $10,795 $12,217 Mar 19 $13,464 $13,267 $11,003 $12,403 Apr 19 $13,795 $13,715 $11,005 $12,655 May 19 $13,403 $12,901 $11,201 $12,295 Jun 19 $13,978 $13,746 $11,341 $12,840 Jul 19 $14,092 $13,786 $11,366 $12,874 Aug 19 $14,005 $13,459 $11,661 $12,824 Sep 19 $14,118 $13,742 $11,599 $12,958 Oct 19 $14,301 $14,119 $11,634 $13,187 Nov 19 $14,615 $14,463 $11,628 $13,377 Dec 19 $14,869 $14,973 $11,620 $13,656 Jan 20 $15,010 $14,807 $11,843 $13,671 Feb 20 $14,288 $13,611 $12,056 $13,107 Mar 20 $12,891 $11,774 $11,985 $12,014 Apr 20 $14,138 $13,035 $12,198 $12,872 May 20 $14,654 $13,602 $12,255 $13,232 Jun 20 $14,926 $14,036 $12,332 $13,519 Jul 20 $15,537 $14,779 $12,517 $14,028 Aug 20 $16,235 $15,683 $12,416 $14,498 Sep 20 $15,857 $15,178 $12,409 $14,215 Oct 20 $15,527 $14,809 $12,353 $13,982 Nov 20 $16,754 $16,634 $12,475 $15,071 Dec 20 $17,211 $17,406 $12,492 $15,499 Jan 21 $17,057 $17,327 $12,402 $15,412 Feb 21 $17,314 $17,729 $12,223 $15,537 Mar 21 $17,673 $18,202 $12,071 $15,709 Apr 21 $18,329 $18,998 $12,166 $16,170 May 21 $18,462 $19,294 $12,206 $16,343 Jun 21 $18,800 $19,548 $12,291 $16,518 Jul 21 $19,164 $19,682 $12,429 $16,660 Aug 21 $19,445 $20,175 $12,405 $16,897 Sep 21 $18,811 $19,342 $12,298 $16,420 Oct 21 $19,601 $20,329 $12,294 $16,921 Nov 21 $19,549 $19,839 $12,331 $16,697 Dec 21 $20,078 $20,633 $12,299 $17,080 Jan 22 $19,186 $19,620 $12,034 $16,430 Feb 22 $18,656 $19,113 $11,900 $16,102 Mar 22 $18,873 $19,527 $11,569 $16,132 Apr 22 $17,681 $17,964 $11,130 $15,113 May 22 $17,825 $17,985 $11,202 $15,162 Jun 22 $16,778 $16,469 $11,026 $14,300 Jul 22 $17,651 $17,619 $11,296 $15,039 Aug 22 $17,005 $16,970 $10,977 $14,537 Sep 22 $15,752 $15,346 $10,502 $13,451 Oct 22 $16,336 $16,272 $10,366 $13,868 Nov 22 $17,468 $17,534 $10,748 $14,717 Dec 22 $16,914 $16,844 $10,699 $14,343 Jan 23 $17,897 $18,051 $11,028 $15,137 Feb 23 $17,393 $17,534 $10,743 $14,720 Mar 23 $17,934 $18,075 $11,016 $15,142 Apr 23 $18,192 $18,334 $11,083 $15,309 May 23 $17,959 $18,138 $10,962 $15,144 Jun 23 $18,622 $19,191 $10,923 $15,650 Jul 23 $18,990 $19,894 $10,915 $15,989 Aug 23 $18,632 $19,338 $10,846 $15,680 Sep 23 $17,980 $18,538 $10,570 $15,132 Oct 23 $17,586 $17,981 $10,403 $14,764 Nov 23 $18,916 $19,640 $10,874 $15,849 Dec 23 $19,716 $20,584 $11,291 $16,548 Jan 24 $19,754 $20,704 $11,260 $16,588 Feb 24 $20,249 $21,593 $11,101 $16,921 Mar 24 $20,821 $22,271 $11,203 $17,303 Apr 24 $20,262 $21,536 $10,920 $16,785 May 24 $21,101 $22,411 $11,105 $17,308 Jun 24 $21,457 $22,910 $11,210 $17,605 Jul 24 $21,792 $23,279 $11,472 $17,940 Aug 24 $22,271 $23,870 $11,637 $18,316 Sep 24 $22,698 $24,425 $11,793 $18,670 Oct 24 $22,193 $23,877 $11,500 $18,233 Nov 24 $22,763 $24,770 $11,622 $18,719 Dec 24 $22,255 $24,183 $11,432 $18,331 |
| Average Annual Return [Table Text Block] | Average Annual Total Returns 1 Year 5 years 10 Years BlackRock Sustainable Balanced Portfolio ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 12.88 % 8.40 % 8.33 % MSCI All Country World Index ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 17.49 10.06 9.23 Bloomberg U.S. Aggregate Bond Index ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 1.25 (0.33 ) 1.35 60% MSCI All Country World Index / 40% Bloomberg U.S. Aggregate Bond Index ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 10.77 6.06 6.25 |
| 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. |
| Performance Table Market Index Changed [Text Block] | |
| Material Change Description [Text Block] | |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| AssetsNet | $ 454,358,052 |
| Holdings Count | Holding | 1,533 |
| Advisory Fees Paid, Amount | $ 1,674,651 |
| InvestmentCompanyPortfolioTurnover | 104% |
| Additional Fund Statistics [Text Block] | Key Fund statistics Net Assets ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ $454,358,052 Number of Portfolio Holdings ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 1,533 Net Investment Advisory Fees ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ $1,674,651 Portfolio Turnover Rate ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 104% |
| Holdings [Text Block] | Portfolio composition Investment Type Percent of Total Investments Footnote Reference (a) Common Stocks ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 61.2 % Corporate Bonds ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 18.8 U.S. Treasury Obligations ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 11.0 U.S. Government Sponsored Agency Securities ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 7.4 Investment Companies ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 1.1 Asset-Backed Securities ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 0.2 Non-Agency Mortgage-Backed Securities ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 0.1 Preferred Securities ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 0.1 Foreign Government Obligations ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 0.1 Other Interests ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ - Footnote Description Footnote (a) Excludes short-term securities, short investments and options, if any. |
