Investment Securities - AFS debt securities in unrealized loss position (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	$ 2,787,798	$ 450,517
Unrealized Loss, Less than 12 Months	49,598	1,893
Fair Value, 12 Months or More	164,323	54,194
Unrealized Loss, 12 Months or More	6,700	605
Fair Value, Total	2,952,121	504,711
Unrealized Loss, Total	56,298	2,498
U.S. Treasuries
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	111,606
Unrealized Loss, Less than 12 Months	2,168
Fair Value, 12 Months or More	0
Unrealized Loss, 12 Months or More	0
Fair Value, Total	111,606
Unrealized Loss, Total	2,168
U.S. Government agencies & GSEs
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	132,893	27,952
Unrealized Loss, Less than 12 Months	2,591	324
Fair Value, 12 Months or More	20,093	607
Unrealized Loss, 12 Months or More	837	1
Fair Value, Total	152,986	28,559
Unrealized Loss, Total	3,428	325
State and political subdivisions
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	69,302	9,402
Unrealized Loss, Less than 12 Months	2,581	49
Fair Value, 12 Months or More	3,148	0
Unrealized Loss, 12 Months or More	81	0
Fair Value, Total	72,450	9,402
Unrealized Loss, Total	2,662	49
Residential MBS, Agency & GSE
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	1,534,744	232,199
Unrealized Loss, Less than 12 Months	25,799	766
Fair Value, 12 Months or More	74,481	0
Unrealized Loss, 12 Months or More	2,722	0
Fair Value, Total	1,609,225	232,199
Unrealized Loss, Total	28,521	766
Residential MBS, Non-agency
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	12,608	2,331
Unrealized Loss, Less than 12 Months	4	128
Fair Value, 12 Months or More	0	0
Unrealized Loss, 12 Months or More	0	0
Fair Value, Total	12,608	2,331
Unrealized Loss, Total	4	128
Commercial MBS, Agency & GSE
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	582,235	89,918
Unrealized Loss, Less than 12 Months	13,098	597
Fair Value, 12 Months or More	66,014	0
Unrealized Loss, 12 Months or More	3,058	0
Fair Value, Total	648,249	89,918
Unrealized Loss, Total	16,156	597
Corporate bonds
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	149,246	1,410
Unrealized Loss, Less than 12 Months	1,811	1
Fair Value, 12 Months or More	16	0
Unrealized Loss, 12 Months or More	1	0
Fair Value, Total	149,262	1,410
Unrealized Loss, Total	1,812	1
Asset-backed securities
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	195,164	87,305
Unrealized Loss, Less than 12 Months	1,546	28
Fair Value, 12 Months or More	571	53,587
Unrealized Loss, 12 Months or More	1	604
Fair Value, Total	195,735	140,892
Unrealized Loss, Total	$ 1,547	$ 632