Separate Account Balances - Separate Account Liabilities (Details) - USD ($) $ in Millions |
Sep. 30, 2026 |
Dec. 31, 2025 |
Dec. 31, 2024 |
|---|---|---|---|
| Separate Account Balances | |||
| Separate account liabilities | $ 194,816.2 | $ 193,622.6 | |
| Other balances | |||
| Separate Account Balances | |||
| Separate account liabilities | 328.0 | 325.0 | |
| Retirement and Income Solutions | |||
| Separate Account Balances | |||
| Separate account liabilities | 145,976.2 | 144,039.2 | |
| Retirement and Income Solutions | Group retirement contracts | |||
| Separate Account Balances | |||
| Separate account liabilities | 139,372.4 | 136,674.3 | $ 125,103.1 |
| Retirement and Income Solutions | Individual variable annuities | |||
| Separate Account Balances | |||
| Separate account liabilities | 6,603.8 | 7,364.9 | 8,334.9 |
| Principal Asset Management | International Pension | Pension | Latin America | |||
| Separate Account Balances | |||
| Separate account liabilities | 40,182.8 | 41,450.5 | 32,802.2 |
| Benefits and Protection | Life Insurance | Universal life | |||
| Separate Account Balances | |||
| Separate account liabilities | $ 8,329.2 | $ 7,807.9 | $ 6,806.7 |