Income Taxes - Reconciliation of Effective Tax Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Amount
U.S. Federal Statutory Tax Rate (21%)	$ 42.2	$ 27.0	$ 11.2
Tax Jurisdiction of Domicile [Extensible Enumeration]	UNITED STATES	UNITED STATES	UNITED STATES
State and Local Income Taxes, Net of Federal Income Tax Effect	$ 0.9	$ 1.0	$ (0.1)
Tax Credits	(1.5)	0.0	0.0
Nontaxable or Nondeductible Items
Compensation Deduction Limitation	2.0	2.7	0.8
Dividend Received Deduction	(2.3)	(2.0)	(1.3)
Prior Year Adjustments	0.3	(0.4)	0.3
Research and Development Reserve	0.0	0.0	(0.2)
Share-Based Payment Awards	(0.5)	(0.2)	0.1
Tax-Exempt Interest Income	(2.4)	(2.5)	(2.7)
Other	0.4	0.2	0.2
Effective Tax Rate	$ 39.1	$ 25.8	$ 8.3
% of Pretax Income
U.S. Federal Statutory Tax Rate (21%)	21.00%	21.00%	21.00%
State and Local Income Taxes, Net of Federal Income Tax Effect	0.40%	0.80%	(0.20%)
Tax Credits	(0.70%)	0.00%	0.00%
Nontaxable or Nondeductible Items
Compensation Deduction Limitation	1.00%	2.10%	1.50%
Dividend Received Deduction	(1.10%)	(1.60%)	(2.40%)
Prior Year Adjustments	0.10%	(0.30%)	0.60%
Research and Development Reserve	0.00%	0.00%	(0.40%)
Share-Based Payment Awards	(0.20%)	(0.20%)	0.20%
Tax-Exempt Interest Income	(1.20%)	(1.90%)	(5.10%)
Other	0.20%	0.20%	0.40%
Effective Tax Rate	19.50%	20.10%	15.60%