v3.26.1
S000003863 [Member] Average Annual Total Returns
 12 Months Ended 60 Months Ended 120 Months Ended
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
MSCI All Country World Index (Net) (Reflects no deduction for fees, expenses or taxes, except for withholding taxes on reinvested dividends)      
Prospectus [Line Items]      
Average Annual Return, Percent [1] 22.34% 11.19% 11.72%
Bloomberg U.S. Aggregate Bond Index (Reflects no deduction for fees, expenses or taxes)      
Prospectus [Line Items]      
Average Annual Return, Percent 7.30% (0.36%) 2.01%
60% MSCI All Country World Index (Net)/40% Bloomberg U.S. Aggregate Bond Index (Reflects no deduction for fees, expenses or taxes, except for withholding taxes on reinvested dividends for net indexes)      
Prospectus [Line Items]      
Average Annual Return, Percent [1] 16.22% 6.57% 7.96%
BlackRock Balanced Portfolio      
Prospectus [Line Items]      
Average Annual Return, Percent 15.67% 8.39% 9.86%
[1] Returns for net indices generally assume the reinvestment of dividends after the deduction of the maximum withholding tax in each country applicable to non-residents of the country as determined by the index provider. Such indices use withholding tax rates that are often at a higher rate than the rates to which the Fund is subject in each country, including for countries where the Fund is not subject to withholding taxes. When this is the case, index performance will be lower than if the index used the Fund’s applicable withholding tax rates, if any. For additional comparative performance information for the MSCI All Country World Index, please see the Fund’s Statement of Additional Information.