Borrowing Arrangements - Collateral value of loans and securities pledged (Details) - Line of credit - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Borrowing Arrangements
Collateral value	$ 2,960,186	$ 3,259,013
Total Available	2,277,460	2,446,504
Remaining Available	2,277,460	2,446,504
FHLB collateralized borrowing capacity
Borrowing Arrangements
Collateral value	1,204,712	1,600,371
Total Available	765,134	1,100,931
Remaining Available	765,134	1,100,931
FRB discount window collateralized line of credit
Borrowing Arrangements
Collateral value	1,755,474	1,658,642
Total Available	1,397,326	1,235,573
Remaining Available	1,397,326	1,235,573
Federal funds purchase arrangements
Borrowing Arrangements
Total Available	90,000	90,000
Remaining Available	90,000	90,000
Holding company line of credit
Borrowing Arrangements
Total Available	25,000	20,000
Remaining Available	$ 25,000	$ 20,000