Debt Securities, Available-for-sale, Allowance for Credit Losses Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Debt Securities, Available-for-Sale, Allowance for Credit Loss [Roll Forward]
Debt Securities, Available-for-sale, Allowance for Credit Loss, Beginning Balance	$ 2.2	$ 0.0
Debt Securities, Available-for-sale, Credit losses on securities for which credit losses were not previously recorded		0.0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Ending Balance	2.2	$ 0.0
All Other Corporate Bonds
Debt Securities, Available-for-Sale, Allowance for Credit Loss [Roll Forward]
Debt Securities, Available-for-sale, Allowance for Credit Loss, Beginning Balance	2.2
Debt Securities, Available-for-sale, Credit losses on securities for which credit losses were not previously recorded	0.0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Ending Balance	$ 2.2