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Securities Securities - Narrative (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Mar. 31, 2022
Mar. 31, 2020
Sep. 30, 2018
Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]            
Available-for-sale securities transferred to Held-to-Maturity     $ 1,100,000 $ 873,600 $ 179,800  
Unrealized after tax gain (loss) on available for sale securities transferred to the held to maturity portfolio     $ 1,500 $ 69,000 $ (2,200)  
Secured borrowing under agreement to repurchase $ 201,400          
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss 262,762         $ 258,224
Debt Securities, Available-for-sale, Unrealized Loss Position 3,246,667         $ 3,265,473
Sales 0 $ 0        
Securities pledged as collateral            
Debt Securities, Available-for-sale [Line Items]            
Financial Instruments, Owned, at Fair Value 2,000,000          
Securities pledged as collateral            
Debt Securities, Available-for-sale [Line Items]            
Secured borrowing under agreement to repurchase $ 201,400