Available-For-Sale And Held-To-Maturity Securities (Narrative) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2024 USD ($) Security	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) Security	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Debt Securities Available For Sale Allowance For CreditLoss	$ 0		$ 0
Accrued interest receivable	100,900,000		100,900,000		$ 94,000,000
Proceeds from sale of available-for-sale securities	0	$ 0	0	$ 2,400,000
Net realized gains (loss) resulting from sale of available-for-sale securities				$ 7,600,000
Financial instruments pledged as collateral	$ 897,500,000		$ 897,500,000		746,400,000
Number of available for sale securities whose amortized costs exceeded their fair values | Security	243		243
Available-for-sale Securities, Continuous	$ 135,402,000		$ 135,402,000
Available-for-sale Securities, Continuous Unrealized	135,104,000		135,104,000
Available-for-sale Securities, Continuous	$ 1,353,173,000		$ 1,353,173,000
Percentage of available-for-sale portfolio	83.60%		83.60%
Pledged [Member]
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Trading securities pledged	$ 1,800,000,000		$ 1,800,000,000		1,300,000,000
Other Assets [Member]
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Accrued interest receivable	$ 99,100,000		$ 99,100,000		$ 95,700,000