v3.25.4
Shareholder Report, Line Graph (Details) - USD ($)
 12 Months Ended 24 Months Ended 36 Months Ended 48 Months Ended 60 Months Ended 72 Months Ended 84 Months Ended 96 Months Ended 108 Months Ended 120 Months Ended
Dec. 31, 2015
Dec. 31, 2025
Dec. 31, 2016
Dec. 31, 2017
Dec. 31, 2018
Dec. 31, 2019
Dec. 31, 2020
Dec. 31, 2021
Dec. 31, 2022
Dec. 31, 2023
Dec. 31, 2024
Dec. 31, 2025
C000013875 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Nuveen Life Growth Equity Fund at NAV                    
Accumulated Value $ 10,000   $ 9,904 $ 13,325 $ 13,297 $ 17,383 $ 25,025 $ 29,070 $ 19,500 $ 28,553 $ 36,624 $ 42,228
C000013877 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Nuveen Life Core Equity Fund at NAV                    
Accumulated Value 10,000   10,860 13,456 12,481 16,238 19,557 24,480 19,036 25,304 32,598 37,096
C000013878 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Nuveen Life International Equity Fund at NAV                    
Accumulated Value 10,000   10,106 13,438 10,270 12,640 14,579 16,159 13,460 15,669 16,240 21,508
C000013879 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Nuveen Life Large Cap Value Fund at NAV                    
Accumulated Value 10,000   11,874 13,340 11,455 14,738 15,328 19,444 18,064 20,648 23,699 27,783
C000013880 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Nuveen Life Small Cap Equity Fund at NAV                    
Accumulated Value 10,000   11,987 13,773 12,114 14,987 16,906 21,091 17,795 21,114 24,493 28,509
C000013881 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Nuveen Life Stock Index Fund at NAV                    
Accumulated Value 10,000   11,271 13,640 12,920 16,902 20,411 25,642 20,723 26,091 32,268 37,766
C000013882 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Nuveen Life Large Cap Responsible Equity Fund at NAV                    
Accumulated Value 10,000   11,335 13,710 12,950 17,014 20,496 25,897 21,280 26,049 30,743 35,856
C000013883 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Nuveen Life Real Estate Securities Select Fund at NAV                    
Accumulated Value 10,000   10,396 11,677 11,183 14,687 14,873 20,752 14,812 16,591 17,385 17,708
C000013884 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Nuveen Life Core Bond Fund at NAV                    
Accumulated Value 10,000   10,423 10,897 10,811 11,835 12,765 12,639 10,970 11,658 11,974 12,820
C000135632 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Nuveen Life Balanced Fund at NAV                    
Accumulated Value 10,000   10,614 12,080 11,420 13,568 15,490 17,005 14,185 16,421 18,125 20,428
Russell 1000 Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Russell 1000® Index                    
Accumulated Value 10,000   11,205 13,636 12,983 17,063 20,640 26,101 21,108 26,708 33,255 39,030
Standard & Poor's 500 Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   S&P 500® Index                    
Accumulated Value 10,000   11,196 13,640 13,042 17,149 20,304 26,132 21,399 27,025 33,786 39,827
MSCI EAFE Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   MSCI EAFE® Index                    
Accumulated Value 10,000   10,100 12,628 10,887 13,284 14,322 15,935 13,632 16,118 16,735 21,959
Russell 3000 Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Russell 3000® Index                    
Accumulated Value 10,000   11,274 13,656 12,940 16,954 20,495 25,754 20,808 26,209 32,448 38,012
Bloomberg U S Aggregate Bond C000013884 Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Bloomberg U.S. Aggregate Bond Index                    
Accumulated Value 10,000   10,265 10,628 10,630 11,556 12,424 12,232 10,641 11,229 11,369 12,199
Russell 1000 Growth Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Russell 1000® Growth Index                    
Accumulated Value 10,000   10,708 13,943 13,732 18,729 25,938 33,096 23,453 33,462 44,623 52,906
Russell 1000 Value Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Russell 1000® Value Index                    
Accumulated Value 10,000   11,734 13,337 12,235 15,482 15,915 19,919 18,418 20,529 23,478 27,213
Russell 2000 Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Russell 2000® Index                    
Accumulated Value 10,000   12,131 13,908 12,376 15,535 18,636 21,397 17,024 19,906 22,203 25,047
FTSE Nareit All Equity REITs Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   FTSE Nareit All Equity REITs Index                    
Accumulated Value 10,000   10,863 11,805 11,328 14,575 13,828 19,539 14,664 16,330 17,133 17,522
Bloomberg U S Aggregate Bond Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Bloomberg U.S. Aggregate Bond Index                    
Accumulated Value 10,000   10,265 10,628 10,630 11,556 12,424 12,232 10,641 11,229 11,369 12,199
Morningstar Moderately Conservative Target Risk Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Morningstar Moderately Conservative Target Risk Index                    
Accumulated Value 10,000   10,666 11,824 11,486 13,238 14,807 15,750 13,568 15,046 16,010 18,070
Balanced Fund Composite Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Balanced Fund Composite Index                    
Accumulated Value $ 10,000   $ 10,663 $ 11,986 $ 11,596 $ 13,781 $ 15,664 $ 17,245 $ 14,599 $ 16,749 $ 18,451 $ 20,960