Allowance for Credit Losses (Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
(Release of) Provision for Credit Losses	$ (15,000,000.0)	$ 3,200,000	$ (500,000)	$ 4,800,000
Net recoveries (charge-offs)	0	(5,500,000)	$ 2,900,000	(8,700,000)
Time period used for projecting future conditions to estimate credit losses			2 years
Other financial assets, allowance for credit loss	1,000,000.0	1,100,000	$ 1,000,000.0	1,100,000	$ 1,000,000.0	$ 800,000	$ 1,100,000	$ 1,000,000.0
Corporate Debt
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
(Release of) Provision for Credit Losses	$ (500,000)	$ 1,300,000	$ 0	$ 1,700,000