Investment Securities - AFS Debt Securities in Unrealized Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	$ 570,148	$ 306,266
Unrealized Loss, Less than 12 Months	2,889	3,515
Fair Value, 12 Months or More	2,550,246	2,587,704
Unrealized Loss, 12 Months or More	256,263	247,106
Fair Value, Total	3,120,394	2,893,970
Unrealized Loss, Total	259,152	250,621
U.S. Treasuries
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	270,743	100,369
Unrealized Loss, Less than 12 Months	1,566	39
Fair Value, 12 Months or More	102,963	103,535
Unrealized Loss, 12 Months or More	11,299	10,672
Fair Value, Total	373,706	203,904
Unrealized Loss, Total	12,865	10,711
U.S. Government agencies & GSEs
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	40,825	41,960
Unrealized Loss, Less than 12 Months	216	141
Fair Value, 12 Months or More	177,406	184,184
Unrealized Loss, 12 Months or More	15,025	14,336
Fair Value, Total	218,231	226,144
Unrealized Loss, Total	15,241	14,477
State and political subdivisions
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	0	0
Unrealized Loss, Less than 12 Months	0	0
Fair Value, 12 Months or More	162,495	163,278
Unrealized Loss, 12 Months or More	18,566	18,502
Fair Value, Total	162,495	163,278
Unrealized Loss, Total	18,566	18,502
Residential MBS, Agency & GSEs
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	81,990	50,014
Unrealized Loss, Less than 12 Months	331	672
Fair Value, 12 Months or More	1,086,333	1,108,290
Unrealized Loss, 12 Months or More	131,902	124,340
Fair Value, Total	1,168,323	1,158,304
Unrealized Loss, Total	132,233	125,012
Residential MBS, Non-agency
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	0	0
Unrealized Loss, Less than 12 Months	0	0
Fair Value, 12 Months or More	312,372	317,247
Unrealized Loss, 12 Months or More	20,673	22,084
Fair Value, Total	312,372	317,247
Unrealized Loss, Total	20,673	22,084
Commercial MBS, Agency & GSEs
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	170,175	98,052
Unrealized Loss, Less than 12 Months	724	2,494
Fair Value, 12 Months or More	379,980	342,390
Unrealized Loss, 12 Months or More	38,929	36,523
Fair Value, Total	550,155	440,442
Unrealized Loss, Total	39,653	39,017
Commercial MBS, Non-agency
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	0	0
Unrealized Loss, Less than 12 Months	0	0
Fair Value, 12 Months or More	19,623	23,594
Unrealized Loss, 12 Months or More	542	675
Fair Value, Total	19,623	23,594
Unrealized Loss, Total	542	675
Corporate bonds
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	3,201	4,016
Unrealized Loss, Less than 12 Months	49	116
Fair Value, 12 Months or More	190,753	195,329
Unrealized Loss, 12 Months or More	17,552	17,011
Fair Value, Total	193,954	199,345
Unrealized Loss, Total	17,601	17,127
Asset-backed securities
Summary of AFS debt securities in an unrealized loss position
Fair Value, Less than 12 Months	3,214	11,855
Unrealized Loss, Less than 12 Months	3	53
Fair Value, 12 Months or More	118,321	149,857
Unrealized Loss, 12 Months or More	1,775	2,963
Fair Value, Total	121,535	161,712
Unrealized Loss, Total	$ 1,778	$ 3,016