Shareholder Report, Average Annual Return (Details)
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12 Months Ended |
60 Months Ended |
120 Months Ended |
Dec. 31, 2025 |
Dec. 31, 2025 |
Dec. 31, 2025 |
| C000013875 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Nuveen Life Growth Equity Fund at NAV
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| Average Annual Return, Percent |
15.30%
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11.03%
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15.49%
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| C000013877 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Nuveen Life Core Equity Fund at NAV
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| Average Annual Return, Percent |
13.80%
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13.66%
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14.01%
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| C000013878 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Nuveen Life International Equity Fund at NAV
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| Average Annual Return, Percent |
32.44%
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8.09%
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7.96%
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| C000013879 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Nuveen Life Large Cap Value Fund at NAV
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| Average Annual Return, Percent |
17.23%
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12.63%
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10.76%
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| C000013880 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Nuveen Life Small Cap Equity Fund at NAV
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| Average Annual Return, Percent |
16.40%
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11.02%
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11.04%
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| C000013881 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Nuveen Life Stock Index Fund at NAV
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| Average Annual Return, Percent |
17.04%
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13.10%
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14.21%
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| C000013882 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Nuveen Life Large Cap Responsible Equity Fund at NAV
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| Average Annual Return, Percent |
16.63%
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11.83%
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13.62%
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| C000013883 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Nuveen Life Real Estate Securities Select Fund at NAV
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| Average Annual Return, Percent |
1.86%
|
3.55%
|
5.88%
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| C000013884 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Nuveen Life Core Bond Fund at NAV
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| Average Annual Return, Percent |
7.07%
|
0.09%
|
2.52%
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| C000135632 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Nuveen Life Balanced Fund at NAV
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| Average Annual Return, Percent |
12.71%
|
5.69%
|
7.40%
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| Russell 1000 Index [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Russell 1000® Index
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| Average Annual Return, Percent |
17.37%
|
13.59%
|
14.59%
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| Standard & Poor's 500 Index [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
S&P 500® Index
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| Average Annual Return, Percent |
17.88%
|
14.42%
|
14.82%
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| MSCI EAFE Index [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
MSCI EAFE® Index
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| Average Annual Return, Percent |
31.22%
|
8.92%
|
8.18%
|
| Russell 3000 Index [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Russell 3000® Index
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| Average Annual Return, Percent |
17.15%
|
13.15%
|
14.29%
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| Bloomberg U S Aggregate Bond C000013884 Index [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Bloomberg U.S. Aggregate Bond Index
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| Average Annual Return, Percent |
7.30%
|
(0.36%)
|
2.01%
|
| Russell 1000 Growth Index [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Russell 1000® Growth Index
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| Average Annual Return, Percent |
18.56%
|
15.32%
|
18.13%
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| Russell 1000 Value Index [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Russell 1000® Value Index
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| Average Annual Return, Percent |
15.91%
|
11.33%
|
10.53%
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| Russell 2000 Index [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Russell 2000® Index
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| Average Annual Return, Percent |
12.81%
|
6.09%
|
9.62%
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| FTSE Nareit All Equity REITs Index [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
FTSE Nareit All Equity REITs Index
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| Average Annual Return, Percent |
2.27%
|
4.85%
|
5.77%
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| Bloomberg U S Aggregate Bond Index [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Bloomberg U.S. Aggregate Bond Index
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| Average Annual Return, Percent |
7.30%
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(0.36%)
|
2.01%
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| Morningstar Moderately Conservative Target Risk Index [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Morningstar Moderately Conservative Target Risk Index
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| Average Annual Return, Percent |
12.87%
|
4.06%
|
6.10%
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| Balanced Fund Composite Index [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Balanced Fund Composite Index
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| Average Annual Return, Percent |
13.60%
|
6.00%
|
7.68%
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