Allowance for Credit Losses (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Provision for credit losses	$ 14.5	$ 1.6
Net recoveries (charge-offs)	$ 2.9	(3.2)
Time period used for projecting future conditions to estimate credit losses	2 years
Other financial assets, allowance for credit loss	$ 1.0	1.1	$ 0.8	$ 1.0
Corporate Debt
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Provision for credit losses	$ 0.5	$ 0.4