Available-for-Sale and Held-to-Maturity Securities (Narrative) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2025 USD ($) Security	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($) Security	Jun. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)	Dec. 21, 2024 USD ($)
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Allowance for credit losses	$ 0		$ 0
Accrued interest receivable	90,600,000		90,600,000			$ 92,600,000
Proceeds from sale of available-for-sale securities	0	$ 0	0	$ 0
Financial instruments pledged as collateral	$ 818,300,000		$ 818,300,000		$ 842,300,000
Number of available for sale securities whose amortized costs exceeded their fair values | Security	227		227
Available-for-sale Securities, Continuous	$ 132,065,000		$ 132,065,000
Available-for-sale Securities, Continuous Unrealized	131,460,000		131,460,000
Available-for-sale Securities, Continuous	$ 1,206,523,000		$ 1,206,523,000
Percentage of available-for-sale portfolio	78.00%		78.00%
Pledged [Member]
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Trading securities pledged	$ 2,500,000,000		$ 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	$ 95,500,000		$ 95,500,000		$ 106,800,000