| Assets | — | — |
| Investments | — | — |
| Fixed maturity securities available for sale, at fair value (amortized cost - $7,524.8 and $7,292.4 at december 31, 2024 and 2023, respectively) | 7,175.1a | 6,912.1a |
| Equity securities at fair value | 208.5a | 223a |
| Commercial mortgage loans on real estate, at amortized cost (net of allowances for credit losses of $6.5 and $4.0 at december 31, 2024 and 2023, respectively) | 342.5a | 328.7a |
| Short-term investments | 281.6a | 258.1a |
| Other investments | 536.8a | 499a |
| Total investments | 8,544.5a | 8,220.9a |
| Cash and cash equivalents | 1,807.7a | 1,627.4a |
| Premiums and accounts receivable (net of allowances for credit losses of $7.2 and $9.0 at december 31, 2024 and 2023, respectively) | 2,054a | 2,265.6a |
| Reinsurance recoverables (net of allowances for credit losses of $5.0 and $4.8 at december 31, 2024 and 2023, respectively) | 7,579.5a | 6,649.2a |
| Accrued investment income | 130.5a | 97a |
| Deferred acquisition costs | 9,992.8a | 9,967.2a |
| Property and equipment, net | 768.3a | 685.8a |
| Goodwill | 2,616a | 2,608.8a |
| Value of business acquired | 8a | 83.9a |
| Other intangible assets, net | 535.6a | 567.1a |
| Other assets (net of allowances for credit losses of $0.6 and $0.7 at december 31, 2024 and 2023, respectively) | 983.7a | 862.3a |
| Total assets | 35,020.6a | 33,635.2a |
| Liabilities | — | — |
| Future policy benefits and expenses | 536.7a | 487.2a |
| Unearned premiums | 20,211.4a | 20,110.4a |
| Claims and benefits payable | 2,914.2a | 1,989.2a |
| Commissions payable | 559.6a | 542.8a |
| Reinsurance balances payable | 493.2a | 430.1a |
| Funds held under reinsurance | 277.7a | 392.7a |
| Accounts payable and other liabilities (including allowances for credit losses of $1.4 and $8.3 at december 31, 2024 and 2023) | 2,838a | 2,792.7a |
| Debt | 2,083.1a | 2,080.6a |
| Total liabilities | 29,913.9a | 28,825.7a |
| Stockholders’ equity | — | — |
| Common stock, par value $0.01 per share, 800,000,000 shares authorized, 53,129,838 and 54,252,083 shares issued and 50,833,749 and 51,955,994 shares outstanding at december 31, 2024 and 2023, respectively | 0.5a | 0.6a |
| Additional paid-in capital | 1,686.8a | 1,668.5a |
| Retained earnings | 4,378.3a | 4,028.2a |
| Accumulated other comprehensive loss | -836.1a | -765a |
| Treasury stock, at cost; 2,296,089 shares at december 31, 2024 and 2023 | -122.8a | -122.8a |
| Total equity | 5,106.7a | 4,809.5a |
| Total liabilities and equity | 35,020.6a | 33,635.2a |