Income Taxes - Statutory Federal Income Tax Expense, Effective Income Tax Expense, Rates (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Amount
Statutory Federal Income Tax Expense (Benefit)	$ 81.6	$ (72.8)	$ (77.9)
Tax-exempt Income and Dividends Received Deduction	(3.4)	(4.8)	(5.3)
Untaxed Earnings on Company-Owned Life Insurance	(7.5)	(6.1)	(8.0)
Tax credits	(1.2)	(3.1)	(6.5)
Stock-Based Compensation	(0.1)	0.3	1.3
Nondeductible Executive Compensation	3.5	1.8	1.5
Goodwill impairment	0.0	6.3	0.0
Expense on Transactions	0.0	0.0	11.5
Effect of foreign operations	(11.3)	(27.4)	0.0
Change in valuation allowance	11.3	27.4	0.0
Other, Net	3.1	3.6	(1.0)
Income Tax Expense (Benefit)	$ 76.0	$ (74.8)	$ (84.4)
Rate
Statutory Federal Income Tax Expense (Benefit)	21.00%	21.00%	21.00%
Tax-exempt Income and Dividends Received Deduction	(0.90%)	1.40%	1.30%
Untaxed Earnings on Company-Owned Life Insurance	(1.90%)	1.80%	2.10%
Tax credits	(0.30%)	0.90%	1.70%
Stock-Based Compensation	0.00%	0.10%	0.30%
Nondeductible Executive Compensation	(0.90%)	0.50%	0.40%
Goodwill impairment	0.00%	(1.80%)	0.00%
Expense on Transactions	0.00%	0.00%	3.00%
Effect of foreign operations	(2.90%)	7.90%	0.00%
Change in valuation allowance	2.90%	(7.90%)	0.00%
Other, Net	(0.80%)	1.10%	(0.30%)
Effective Income Tax Expense (Benefit)	19.60%	21.60%	22.70%