Investments Purchased with Collateral from Securities Lending [Member] Russell 1000 Growth Index [Member] Russell 1000 Index [Member] C000013875 [Member] Nuveen Life Growth Equity Fund Common Stock [Member] Repurchase Agreements [Member] C000013876 [Member] Nuveen Life Money Market Fund Short Term Treasury Debt [Member] Short Term Variable Rate securities [Member] Short Term Government Agency Debt [Member] C000013877 [Member] Nuveen Life Core Equity Fund Standard & Poor's 500 Index [Member] AUSTRALIA DENMARK FRANCE GERMANY JAPAN NETHERLANDS SPAIN SWITZERLAND UNITED KINGDOM UNITED STATES C000013878 [Member] Nuveen Life International Equity Fund MSCI EAFE Index [Member] Other [Member] Russell 1000 Value Index [Member] C000013879 [Member] Nuveen Life Large Cap Value Fund C000013880 [Member] Nuveen Life Small Cap Equity Fund Russell 3000 Index [Member] Russell 2000 Index [Member] Rights Warrants [Member] C000013881 [Member] Nuveen Life Stock Index Fund C000013882 [Member] Nuveen Life Large Cap Responsible Equity Fund Investment Companies [Member] FTSE Nareit All Equity REITs Index [Member] C000013883 [Member] Nuveen Life Real Estate Securities Select Fund Bank Loan Obligations [Member] Moody's, Aaa Rating [Member] Standard & Poor's, AA Rating [Member] Standard & Poor's, A Rating [Member] Standard & Poor's, BBB Rating [Member] Corporate Bond Securities [Member] Preferred Stock [Member] C000013884 [Member] Nuveen Life Core Bond Fund Bloomberg U S Aggregate Bond C000013884 Index [Member] Government Bonds [Member] Structured Assets [Member] N R not rated [Member] N A not applicable [Member] BB or Lower [Member] Bloomberg U S Aggregate Bond Index [Member] Morningstar Moderately Conservative Target Risk Index [Member] Balanced Fund Composite Index [Member] International Equity [Member] U S Equity [Member] C000135632 [Member] Nuveen Life Balanced Fund Fixed Income Securities [Member] Investment Type [Axis] Net Assets Investment Company Portfolio Turnover No Trading Symbol Flag