Available-for-Sale and Held-to-Maturity Securities (Narrative) (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) Security	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Proceeds from sale of available-for-sale securities	$ 2,400,000	$ 80,000,000	$ 0
Net realized gains (loss) resulting from sale of available-for-sale securities	(7,600,000)	100,000
Accrued interest receivable	94,000,000	65,700,000
Financial instruments pledged as collateral	$ 746,400,000	796,200,000
Number of available for sale securities whose amortized costs exceeded their fair values | Security	281
Available-for-sale Securities, Continuous	$ 175,950,000
Available-for-sale Securities, Continuous	1,548,891,000
Available-for-sale Securities, Continuous Unrealized	$ 174,078,000
Percentage of available-for-sale portfolio	99.80%
Pledged [Member]
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Trading securities pledged	$ 1,300,000,000	1,300,000,000
Other Assets [Member]
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Accrued interest receivable	$ 95,700,000	$ 82,300,000