Long-Duration Insurance Contracts - Policyholder Account Balances (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
Dec. 31, 2025 |
|
| Policyholder Account Balance [Roll Forward] | |||||
| Beginning balance | $ 5,064.1 | ||||
| Interest credited | $ 54.6 | $ 52.7 | 108.4 | $ 105.5 | |
| Ending balance | 5,041.8 | 5,041.8 | $ 5,064.1 | ||
| Indexed Universal Life | |||||
| Policyholder Account Balance [Roll Forward] | |||||
| Beginning balance | 100.6 | 78.2 | 95.5 | 72.9 | 72.9 |
| Premiums received | 7.3 | 4.9 | 14.0 | 10.9 | |
| Surrenders and withdrawals | (0.5) | (0.4) | (1.4) | (0.8) | |
| Benefit payments | (0.4) | 0.0 | (0.4) | 0.0 | |
| Net transfers from (to) separate account | 0.2 | (0.1) | (0.1) | (0.2) | |
| Interest credited | 2.0 | 0.8 | 2.8 | 1.8 | |
| Other | (1.3) | (1.1) | (2.5) | (2.3) | |
| Ending balance | $ 107.9 | $ 82.3 | $ 107.9 | $ 82.3 | 95.5 |
| Weighted-average crediting rate | 8.20% | 4.10% | 5.80% | 4.80% | |
| Net amount at risk | $ 0.0 | $ 0.0 | $ 0.0 | $ 0.0 | |
| Cash surrender value | 84.3 | 62.4 | 84.3 | 62.4 | |
| Experience life | |||||
| Policyholder Account Balance [Roll Forward] | |||||
| Beginning balance | 53.7 | 57.4 | 54.8 | 58.0 | 58.0 |
| Premiums received | (0.2) | (0.2) | (0.4) | (0.4) | |
| Surrenders and withdrawals | (1.1) | (1.0) | (2.0) | (1.8) | |
| Benefit payments | (0.3) | (0.4) | (0.8) | (0.7) | |
| Net transfers from (to) separate account | 0.0 | 0.0 | 0.0 | 0.0 | |
| Interest credited | 0.7 | 0.7 | 1.3 | 1.4 | |
| Other | 0.0 | 0.0 | (0.1) | 0.0 | |
| Ending balance | $ 52.8 | $ 56.5 | $ 52.8 | $ 56.5 | 54.8 |
| Weighted-average crediting rate | 5.30% | 5.00% | 4.90% | 5.00% | |
| Net amount at risk | $ 0.0 | $ 0.0 | $ 0.0 | $ 0.0 | |
| Cash surrender value | 52.2 | 55.9 | 52.2 | 55.9 | |
| Fixed Account Annuities | |||||
| Policyholder Account Balance [Roll Forward] | |||||
| Beginning balance | 4,482.6 | 4,495.9 | 4,486.8 | 4,508.4 | 4,508.4 |
| Premiums received | 40.0 | 46.6 | 76.3 | 90.0 | |
| Surrenders and withdrawals | (88.4) | (80.8) | (162.4) | (170.0) | |
| Benefit payments | (17.1) | (21.4) | (32.1) | (43.2) | |
| Net transfers from (to) separate account | 5.3 | 8.2 | 14.2 | 20.2 | |
| Interest credited | 42.7 | 40.9 | 84.1 | 83.6 | |
| Other | 3.9 | 5.7 | 2.1 | 6.1 | |
| Ending balance | $ 4,469.0 | $ 4,495.1 | $ 4,469.0 | $ 4,495.1 | 4,486.8 |
| Weighted-average crediting rate | 3.90% | 3.70% | 3.90% | 3.80% | |
| Net amount at risk | $ 22.2 | $ 24.7 | $ 22.2 | $ 24.7 | |
| Cash surrender value | 4,421.0 | 4,448.7 | 4,421.0 | 4,448.7 | |
| Fixed Indexed Account Annuities | |||||
| Policyholder Account Balance [Roll Forward] | |||||
| Beginning balance | 365.1 | 399.7 | 373.3 | 409.5 | 409.5 |
| Premiums received | 2.8 | 3.4 | 5.7 | 7.6 | |
| Surrenders and withdrawals | (10.1) | (11.2) | (20.0) | (24.4) | |
| Benefit payments | (0.4) | (0.7) | (1.4) | (2.4) | |
| Net transfers from (to) separate account | (0.2) | (0.4) | (0.3) | (0.6) | |
| Interest credited | 5.6 | 2.8 | 7.0 | 6.2 | |
| Other | (2.1) | (5.0) | (3.6) | (7.3) | |
| Ending balance | $ 360.7 | $ 388.6 | $ 360.7 | $ 388.6 | 373.3 |
| Weighted-average crediting rate | 6.40% | 2.90% | 3.90% | 3.20% | |
| Net amount at risk | $ 0.0 | $ 0.0 | $ 0.0 | $ 0.0 | |
| Cash surrender value | 356.9 | 382.7 | 356.9 | 382.7 | |
| SPIA (non-life contingent) | |||||
| Policyholder Account Balance [Roll Forward] | |||||
| Beginning balance | 26.2 | 28.3 | 26.1 | 28.6 | 28.6 |
| Premiums received | 0.8 | 0.8 | 1.9 | 1.4 | |
| Surrenders and withdrawals | (0.2) | 0.0 | (0.3) | (0.2) | |
| Benefit payments | (1.2) | (1.1) | (2.3) | (2.3) | |
| Net transfers from (to) separate account | 0.0 | 0.0 | 0.0 | 0.0 | |
| Interest credited | 0.2 | 0.2 | 0.4 | 0.5 | |
| Other | 0.0 | (0.3) | 0.0 | (0.1) | |
| Ending balance | $ 25.8 | $ 27.9 | $ 25.8 | $ 27.9 | $ 26.1 |
| Weighted-average crediting rate | 3.40% | 2.90% | 3.30% | 3.70% | |
| Net amount at risk | $ 0.0 | $ 0.0 | $ 0.0 | $ 0.0 | |
| Cash surrender value | $ 25.5 | $ 27.6 | $ 25.5 | $ 27.6 | |