Long-Duration Insurance Contracts - Policyholder Account Balances (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|---|
Jun. 30, 2025 |
Jun. 30, 2024 |
Jun. 30, 2025 |
Jun. 30, 2024 |
Dec. 31, 2024 |
|
| Policyholder Account Balance [Roll Forward] | |||||
| Beginning balance | $ 5,100.3 | ||||
| Interest credited | $ 52.7 | $ 53.8 | 105.5 | $ 106.7 | |
| Ending balance | 5,076.4 | 5,076.4 | $ 5,100.3 | ||
| Indexed Universal Life | |||||
| Policyholder Account Balance [Roll Forward] | |||||
| Beginning balance | 78.2 | 61.0 | 72.9 | 57.8 | 57.8 |
| Premiums received | 4.9 | 4.9 | 10.9 | 8.8 | |
| Surrenders and withdrawals | (0.4) | (0.3) | (0.8) | (0.8) | |
| Benefit payments | 0.0 | 0.0 | 0.0 | 0.0 | |
| Net transfers from (to) separate account | (0.1) | 0.0 | (0.2) | (0.1) | |
| Interest credited | 0.8 | 0.8 | 1.8 | 1.6 | |
| Other | (1.1) | (1.2) | (2.3) | (2.1) | |
| Ending balance | $ 82.3 | $ 65.2 | $ 82.3 | $ 65.2 | 72.9 |
| Weighted-average crediting rate | 4.10% | 5.20% | 4.80% | 5.40% | |
| Net amount at risk | $ 0.0 | $ 0.0 | $ 0.0 | $ 0.0 | |
| Cash surrender value | 62.4 | 47.1 | 62.4 | 47.1 | |
| Experience life | |||||
| Policyholder Account Balance [Roll Forward] | |||||
| Beginning balance | 57.4 | 60.1 | 58.0 | 61.2 | 61.2 |
| Premiums received | (0.2) | (0.2) | (0.4) | (0.3) | |
| Surrenders and withdrawals | (1.0) | (0.8) | (1.8) | (2.1) | |
| Benefit payments | (0.4) | (0.4) | (0.7) | (0.9) | |
| Net transfers from (to) separate account | 0.0 | 0.0 | 0.0 | 0.0 | |
| Interest credited | 0.7 | 0.8 | 1.4 | 1.5 | |
| Other | 0.0 | (0.1) | 0.0 | 0.0 | |
| Ending balance | $ 56.5 | $ 59.4 | $ 56.5 | $ 59.4 | 58.0 |
| Weighted-average crediting rate | 5.00% | 5.50% | 5.00% | 5.00% | |
| Net amount at risk | $ 0.0 | $ 0.0 | $ 0.0 | $ 0.0 | |
| Cash surrender value | 55.9 | 58.8 | 55.9 | 58.8 | |
| Fixed Account Annuities | |||||
| Policyholder Account Balance [Roll Forward] | |||||
| Beginning balance | 4,495.9 | 4,519.9 | 4,508.4 | 4,556.0 | 4,556.0 |
| Premiums received | 46.6 | 42.8 | 90.0 | 91.8 | |
| Surrenders and withdrawals | (80.8) | (86.4) | (170.0) | (198.6) | |
| Benefit payments | (21.4) | (16.3) | (43.2) | (36.9) | |
| Net transfers from (to) separate account | 8.2 | 6.3 | 20.2 | 8.2 | |
| Interest credited | 40.9 | 41.3 | 83.6 | 83.0 | |
| Other | 5.7 | 1.9 | 6.1 | 6.0 | |
| Ending balance | $ 4,495.1 | $ 4,509.5 | $ 4,495.1 | $ 4,509.5 | 4,508.4 |
| Weighted-average crediting rate | 3.70% | 3.70% | 3.80% | 3.70% | |
| Net amount at risk | $ 24.7 | $ 30.9 | $ 24.7 | $ 30.9 | |
| Cash surrender value | 4,448.7 | 4,466.3 | 4,448.7 | 4,466.3 | |
| Fixed Indexed Account Annuities | |||||
| Policyholder Account Balance [Roll Forward] | |||||
| Beginning balance | 399.7 | 437.4 | 409.5 | 449.0 | 449.0 |
| Premiums received | 3.4 | 4.1 | 7.6 | 7.7 | |
| Surrenders and withdrawals | (11.2) | (13.5) | (24.4) | (26.8) | |
| Benefit payments | (0.7) | (0.8) | (2.4) | (1.6) | |
| Net transfers from (to) separate account | (0.4) | (0.6) | (0.6) | (1.4) | |
| Interest credited | 2.8 | 3.2 | 6.2 | 5.9 | |
| Other | (5.0) | (3.2) | (7.3) | (6.2) | |
| Ending balance | $ 388.6 | $ 426.6 | $ 388.6 | $ 426.6 | 409.5 |
| Weighted-average crediting rate | 2.90% | 3.00% | 3.20% | 2.70% | |
| Net amount at risk | $ 0.0 | $ 0.0 | $ 0.0 | $ 0.0 | |
| Cash surrender value | 382.7 | 428.4 | 382.7 | 428.4 | |
| SPIA (non-life contingent) | |||||
| Policyholder Account Balance [Roll Forward] | |||||
| Beginning balance | 28.3 | 31.6 | 28.6 | 32.6 | 32.6 |
| Premiums received | 0.8 | 0.1 | 1.4 | 0.9 | |
| Surrenders and withdrawals | 0.0 | (0.3) | (0.2) | (0.9) | |
| Benefit payments | (1.1) | (1.3) | (2.3) | (2.7) | |
| Net transfers from (to) separate account | 0.0 | 0.0 | 0.0 | 0.0 | |
| Interest credited | 0.2 | 0.3 | 0.5 | 0.5 | |
| Other | (0.3) | 0.0 | (0.1) | 0.0 | |
| Ending balance | $ 27.9 | $ 30.4 | $ 27.9 | $ 30.4 | $ 28.6 |
| Weighted-average crediting rate | 2.90% | 3.90% | 3.70% | 3.10% | |
| Net amount at risk | $ 0.0 | $ 0.0 | $ 0.0 | $ 0.0 | |
| Cash surrender value | $ 27.6 | $ 31.4 | $ 27.6 | $ 31.4 | |