Investment Securities - Pledged Securities (Details) - USD ($) $ in Thousands		Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Held-to-maturity	[1]	$ 675,409	$ 560,212
Asset Pledged as Collateral | Securing public and trust department deposits, and repurchase agreements:
Debt Securities, Available-for-sale [Line Items]
Available-for-sale		745,164	779,244
Held-to-maturity		523,317	312,921
Asset Pledged as Collateral | Securing additional borrowing capacity at the FHLB and the FRB:
Debt Securities, Available-for-sale [Line Items]
Available-for-sale		3,520	3,972
Held-to-maturity		$ 1,254	$ 128,870

[1]     Available-for-sale investment securities and held-to-maturity investment securities are presented net of allowance for credit losses of $0 and $238, respectively, at September 30, 2023, and $0 and $241, respectively, at December 31, 2022.