Schedule 2 - Parent Company Financial Statements - Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Amortized cost of fixed maturities	$ 7,295.0	$ 7,565.8
Cost of equity securities	197.1	209.3
Long-term Debt	$ 1,278.4	1,213.4
Senior Notes \| Senior Notes, 4.35 Percent Due February 15, 2025
Stated interest rate, percentage	4.35%
Parent Company
Amortized cost of fixed maturities	$ 0.5	177.4
Cost of equity securities	$ 12.8	11.6
Parent Company \| Senior Notes \| Senior Notes, 4.35 Percent Due February 15, 2025
Stated interest rate, percentage	4.35%
Long-term Debt	$ 448.1	440.8
Parent Company \| Senior Notes \| Senior Notes, 2.400 Percent Due September 30, 2030
Stated interest rate, percentage	2.40%
Long-term Debt	$ 338.9	313.6
Parent Company \| Senior Notes \| Senior Notes, 3.800 Percent Due February 23, 2032
Stated interest rate, percentage	3.80%
Long-term Debt	$ 352.2	338.4
Parent Company \| Junior Debt \| 5.875% Fixed-Rate Reset Junior Subordinated Debentures due 2062
Stated interest rate, percentage	5.875%
Long-term Debt	$ 139.2	$ 120.6

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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