Available-For-Sale And Held-To-Maturity Securities (Narrative) (Details)	12 Months Ended
	Dec. 31, 2021 USD ($) Security	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Proceeds from sale of available-for-sale securities		$ 491,900,000	$ 641,800,000
Net realized gains (loss) resulting from sale of available-for-sale securities	$ 0	(500,000)	$ (300,000)
Accrued interest receivable	27,400,000	20,800,000
Transfers from held to maturity to available for sale securities reclassification fair value	312,900,000	1,000,000,000.0
Gain On Transfer Of securities	0	0
Financial instruments pledged as collateral	$ 639,600,000	368,400,000
Number of available for sale securities whose amortized costs exceeded their fair values | Security	89
Available-for-sale Securities, Continuous	$ 17,026,000
Available-for-sale Securities, Continuous	1,061,879,000
Available-for-sale Securities, Continuous Unrealized	$ 3,479,000
Percentage of available-for-sale portfolio	50.20%
Pledged [Member]
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Trading securities pledged	$ 1,200,000,000	1,400,000,000
Other Assets [Member]
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Accrued interest receivable	$ 29,100,000	$ 26,000,000.0