LifePath Dynamic 2030 Fund Custom Benchmark [Member] Bloomberg U S Aggregate Bond Index [Member] Liabilities in Excess of Other Assets [Member] Equity Funds Securities [Member] BlackRock Real Estate Securities Fund [Member] iShares MSCI EAFE Small Cap ETF [Member] iShares Global Infrastructure ETF [Member] iShares Broad USD Investment Grade Corporate Bond ETF [Member] BlackRock Tactical Opportunities Fund Class K [Member] iShares Core MSCI Emerging Markets ETF [Member] iShares 0 5 Year TIPS Bond ETF [Member] International Tilts Master Portfolio [Member] BlackRock Diversified Fixed Income Fund Class K [Member] Diversified Equity Master Portfolio [Member] Russell 1000 Index [Member] C000082487 [Member] Class R C000051481 [Member] Class K C000088835 [Member] Investor C C000011997 [Member] Investor A C000011998 [Member] Institutional Fixed Income Funds [Member] Money Market Funds [Member] C000012000 [Member] C000011999 [Member] C000088838 [Member] C000051482 [Member] C000082488 [Member] iShares MSCI Canada ETF [Member] LifePath Dynamic 2040 Fund Custom Benchmark [Member] Russell 1000 C000082489 Index [Member] Bloomberg U S Aggregate Bond C000082489 Index [Member] Russell 1000 C000051483 Index [Member] Bloomberg U S Aggregate Bond C000051483 Index [Member] Bloomberg U S Aggregate Bond C000012002 Index [Member] Russell 1000 C000012002 Index [Member] Russell 1000 C000088841 Index [Member] Bloomberg U S Aggregate Bond C000088841 Index [Member] Russell 1000 C000012001 Index [Member] Bloomberg U S Aggregate Bond C000012001 Index [Member] LifePath Dynamic Retirement Fund Custom Benchmark [Member] C000082489 [Member] C000051483 [Member] C000088841 [Member] C000012001 [Member] C000012002 [Member] C000063261 [Member] C000063260 [Member] C000088844 [Member] C000063262 [Member] C000082490 [Member] LifePath Dynamic 2050 Fund Custom Benchmark [Member] iShares Core MSCI International Developed Markets ETF [Member] LifePath Dynamic 2035 Fund Custom Benchmark [Member] C000089952 [Member] C000089956 [Member] C000089954 [Member] C000089953 [Member] C000089955 [Member] C000089959 [Member] C000089957 [Member] C000089958 [Member] C000089960 [Member] C000089961 [Member] LifePath Dynamic 2045 Fund Custom Benchmark [Member] iShares Russell 2000 ETF [Member] LifePath Dynamic 2055 Fund Custom Benchmark [Member] C000089966 [Member] C000089965 [Member] C000089963 [Member] C000089962 [Member] C000089964 [Member] C000187070 [Member] C000187068 [Member] C000187069 [Member] C000187072 [Member] C000187071 [Member] LifePath Dynamic 2060 Fund Custom Benchmark [Member] LifePath Dynamic 2065 Fund Custom Benchmark [Member] C000213847 [Member] C000213844 [Member] C000213843 [Member] C000213845 [Member] C000213846 [Member] C000251825 [Member] C000251826 [Member] C000251827 [Member] C000251828 [Member] C000251824 [Member] LifePath Dynamic 2070 Fund Custom Benchmark [Member] iShares Core MSCI EAFE ETF [Member] iShares MSCI Japan ETF [Member] Investment Type [Axis] Net Assets Investment Company Portfolio Turnover No Trading Symbol Flag