Available-for-Sale and Held-to-Maturity Securities (Narrative) (Details)	3 Months Ended
	Mar. 31, 2025 USD ($) Security	Mar. 31, 2024 USD ($)	Dec. 31, 2024 USD ($)
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Accrued interest receivable	$ 88,800,000		$ 92,600,000
Allowance for credit losses	0
Proceeds from sale of available-for-sale securities	0	$ 0
Financial instruments pledged as collateral	$ 860,400,000		842,300,000
Number of available for sale securities whose amortized costs exceeded their fair values | Security	235
Available-for-sale Securities, Continuous	$ 143,871,000
Available-for-sale Securities, Continuous Unrealized	143,110,000
Available-for-sale Securities, Continuous	$ 1,278,110,000
Percentage of available-for-sale portfolio	79.20%
Pledged [Member]
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Trading securities pledged	$ 2,500,000,000		2,200,000,000
Other Assets [Member]
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Accrued interest receivable	$ 97,200,000		$ 106,800,000