Debt Securities, Available-for-sale, Allowance for Credit Losses Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Debt Securities, Available-for-Sale, Allowance for Credit Loss [Roll Forward]
Balance, Beginning Balance			$ 5.9
Balance, Ending Balance	$ 0.0		0.0
All Other Corporate Bonds
Debt Securities, Available-for-Sale, Allowance for Credit Loss [Roll Forward]
Balance, Beginning Balance	0.0	$ 14.4	5.9	$ 2.8
Debt Securities, Available-for-sale, Credit losses on securities for which credit losses were not previously recorded			0.0	10.5
Debt Securities, Available-for-sale, Allowance for Credit Loss, Sell before Recovery			(5.9)	0.0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Change in allowance due to change in intent to hold securities to maturity	0.0	1.6	0.0	2.7
Debt Securities, Available-for-sale, Allowance for Credit Loss, Securities Sold	0.0	(0.8)	0.0	(0.8)
Balance, Ending Balance	$ 0.0	$ 15.2	$ 0.0	$ 15.2