v3.26.1
Available-for-Sale and Held-to-Maturity Securities (Narrative) (Details)
 3 Months Ended 6 Months Ended
Jun. 30, 2026
USD ($)
Security
Jun. 30, 2025
USD ($)
Jun. 30, 2026
USD ($)
Security
Jun. 30, 2025
USD ($)
Dec. 31, 2025
USD ($)
Security
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]          
Allowance for credit losses $ 0   $ 0    
Accrued interest receivable 92,500,000   92,500,000   $ 90,700,000
Proceeds from sale of available-for-sale securities 0 $ 0 0 $ 0  
Financial instruments pledged as collateral $ 1,200,000,000   $ 1,200,000,000   $ 880,500,000
Number of available for sale securities whose amortized costs exceeded their fair values | Security 219   219   204
Available-for-sale Securities, Continuous $ 118,025,000   $ 118,025,000   $ 110,060,000
Available-for-sale Securities, Continuous Unrealized 111,898,000   111,898,000   108,681,000
Available-for-sale Securities, Continuous $ 1,277,569,000   $ 1,277,569,000   $ 1,155,012,000
Percentage of available-for-sale portfolio 83.50%   83.50%   72.50%
Percentage available for sale securities 88.00%   88.00%    
Pledged [Member]          
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]          
Trading securities pledged $ 3,700,000,000   $ 3,700,000,000   $ 3,300,000,000
Location, Statement of Financial Position, Balance [Axis]: us-gaap:OtherAssets          
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]          
Accrued interest receivable $ 79,500,000   $ 79,500,000   $ 84,100,000