Investment Securities - Amortized cost and fair value by contractual maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Amortized Cost
Due after one year through five years	$ 101,152
Due after five years through ten years	359,629
Due after ten years	2,277,397
Total	2,738,178	$ 1,819,901
Fair Value
Due after one year through five years	92,747
Due after five years through ten years	321,679
Due after ten years	1,884,736
Fair Value	2,299,162	1,778,064
Amortized Cost
Due in one year or less	107,230
Due after one year through five years	487,512
Due after five years through ten years	1,149,845
Due after ten years	4,575,309
Amortized Cost	6,319,896	5,221,296
Fair Value
Due in one year or less	105,253
Due after one year through five years	466,754
Due after five years through ten years	999,829
Due after ten years	3,797,774
Fair Value	$ 5,369,610	$ 5,193,478