Investments Investment Income (Detail) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||||
|---|---|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
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| Net Investment Income | ||||||
| Gross Investment Income, Operating | $ 517.4 | $ 584.8 | $ 1,025.5 | $ 1,122.3 | ||
| Less Investment Expenses | 36.3 | 21.3 | 58.1 | 42.7 | ||
| Less Investment Income on PFA Assets | 2.7 | 2.8 | 5.6 | 5.7 | ||
| Net Investment Income | 478.4 | 560.7 | 961.8 | 1,073.9 | ||
| Fixed Maturity Securities | ||||||
| Net Investment Income | ||||||
| Gross Investment Income, Operating | 443.4 | 477.8 | 868.8 | 941.1 | ||
| Derivatives | ||||||
| Net Investment Income | ||||||
| Gross Investment Income, Operating | 3.8 | 6.1 | 7.4 | 1.9 | ||
| Mortgage Loans | ||||||
| Net Investment Income | ||||||
| Gross Investment Income, Operating | 21.6 | 21.9 | 43.2 | 43.7 | ||
| Policy Loans | ||||||
| Net Investment Income | ||||||
| Gross Investment Income, Operating | 6.0 | 5.7 | 11.3 | 10.9 | ||
| Perpetual Preferred Securities | ||||||
| Net Investment Income | ||||||
| Gross Investment Income, Operating | 0.0 | 0.0 | 0.0 | 0.8 | ||
| Private Equity Partnerships | ||||||
| Net Investment Income | ||||||
| Gross Investment Income, Operating | [1] | 20.8 | 25.3 | 44.0 | 43.6 | |
| Unrealized Gain (Loss) on Investments | 25.8 | 31.2 | 55.5 | 57.6 | ||
| Management Fee Expense | (5.0) | (5.9) | (11.5) | (14.0) | ||
| Other Long-term Investments | ||||||
| Net Investment Income | ||||||
| Gross Investment Income, Operating | 4.7 | 14.9 | 8.9 | 19.2 | ||
| Short-term Investments | ||||||
| Net Investment Income | ||||||
| Gross Investment Income, Operating | $ 17.1 | $ 33.1 | $ 41.9 | $ 61.1 | ||
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