Securities - Amortized Cost and Fair Value of Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Securities available-for-sale [Abstract]
Amortized Cost	$ 4,613,823	$ 4,548,772
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax	27,657	26,982
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax	262,762	258,224
Fair Value	4,378,718	4,317,530
Available-for-sale, Amortized Cost [Abstract]
Due in one year or less	27,863
Due in one year to five years	241,765
Due in five years to ten years	506,600
Due after ten years	2,511,647
Mortgage-backed securities	1,095,839
Asset-backed securities	230,109
Amortized Cost	4,613,823	4,548,772
Available-for-sale, Fair Value [Abstract]
Due in one year or less	29,143
Due in one year to five years	236,003
Due in five years to ten years	462,247
Due after ten years	2,459,445
Mortgage-backed securities	970,212
Asset-backed securities	221,668
Fair Value	4,378,718	4,317,530
Securities held-to-maturity [Abstract]
Amortized Cost	2,994,837	3,008,064
Gross Unrealized Gains	3,007	6,716
Gross Unrealized Losses	264,785	239,596
Fair Value	2,733,059	2,775,184
Allowance for credit losses - securities held-to-maturity	1,708	1,707
Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss	2,993,129	3,006,357
Held-to-maturity, Amortized Cost [Abstract]
Due in one year or less	95,418
Due in one year to five years	372,318
Due in five years to ten years	91,872
Due after ten years	1,859,490
Mortgage-backed securities	378,228
Asset-backed securities	197,511
Amortized Cost	2,994,837	3,008,064
Held-to-maturity, Fair Value [Abstract]
Due in one year or less	92,840
Due in one year to five years	347,867
Due in five years to ten years	84,791
Due after ten years	1,683,161
Mortgage-backed securities	339,269
Asset-backed securities	185,131
Fair Value	2,733,059	2,775,184
U.S. Treasury securities
Securities available-for-sale [Abstract]
Amortized Cost	877,149	907,990
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax	21	2
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax	4,379	14,580
Fair Value	872,791	893,412
Available-for-sale, Amortized Cost [Abstract]
Amortized Cost	877,149	907,990
Available-for-sale, Fair Value [Abstract]
Fair Value	872,791	893,412
Securities held-to-maturity [Abstract]
Amortized Cost	90,199	90,309
Gross Unrealized Gains	0	0
Gross Unrealized Losses	3,415	3,840
Fair Value	86,784	86,469
Held-to-maturity, Amortized Cost [Abstract]
Amortized Cost	90,199	90,309
Held-to-maturity, Fair Value [Abstract]
Fair Value	86,784	86,469
U.S. Government agency securities
Securities available-for-sale [Abstract]
Amortized Cost	316,289	284,607
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax	20	0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax	27,476	21,877
Fair Value	288,833	262,730
Available-for-sale, Amortized Cost [Abstract]
Amortized Cost	316,289	284,607
Available-for-sale, Fair Value [Abstract]
Fair Value	288,833	262,730
Securities held-to-maturity [Abstract]
Amortized Cost	364,898	364,769
Gross Unrealized Gains	0	0
Gross Unrealized Losses	20,355	19,187
Fair Value	344,543	345,582
Held-to-maturity, Amortized Cost [Abstract]
Amortized Cost	364,898	364,769
Held-to-maturity, Fair Value [Abstract]
Fair Value	344,543	345,582
Mortgage-backed securities
Securities available-for-sale [Abstract]
Amortized Cost	1,095,839	1,071,963
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax	544	444
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax	126,171	125,017
Fair Value	970,212	947,390
Available-for-sale, Amortized Cost [Abstract]
Amortized Cost	1,095,839	1,071,963
Available-for-sale, Fair Value [Abstract]
Fair Value	970,212	947,390
Securities held-to-maturity [Abstract]
Amortized Cost	378,228	382,100
Gross Unrealized Gains	175	637
Gross Unrealized Losses	39,134	34,900
Fair Value	339,269	347,837
Held-to-maturity, Amortized Cost [Abstract]
Amortized Cost	378,228	382,100
Held-to-maturity, Fair Value [Abstract]
Fair Value	339,269	347,837
State and municipal securities
Securities available-for-sale [Abstract]
Amortized Cost	1,620,208	1,604,874
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax	26,568	26,129
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax	53,993	45,108
Fair Value	1,592,783	1,585,895
Available-for-sale, Amortized Cost [Abstract]
Amortized Cost	1,620,208	1,604,874
Available-for-sale, Fair Value [Abstract]
Fair Value	1,592,783	1,585,895
Securities held-to-maturity [Abstract]
Amortized Cost	1,878,776	1,886,459
Gross Unrealized Gains	2,783	6,079
Gross Unrealized Losses	180,516	159,027
Fair Value	1,701,043	1,733,511
Held-to-maturity, Amortized Cost [Abstract]
Amortized Cost	1,878,776	1,886,459
Held-to-maturity, Fair Value [Abstract]
Fair Value	1,701,043	1,733,511
Asset-backed securities
Securities available-for-sale [Abstract]
Amortized Cost	230,109	201,577
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax	452	338
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax	8,893	10,280
Fair Value	221,668	191,635
Available-for-sale, Amortized Cost [Abstract]
Amortized Cost	230,109	201,577
Available-for-sale, Fair Value [Abstract]
Fair Value	221,668	191,635
Securities held-to-maturity [Abstract]
Amortized Cost	197,511	198,418
Gross Unrealized Gains	49	0
Gross Unrealized Losses	12,429	14,228
Fair Value	185,131	184,190
Held-to-maturity, Amortized Cost [Abstract]
Amortized Cost	197,511	198,418
Held-to-maturity, Fair Value [Abstract]
Fair Value	185,131	184,190
Corporate notes and other
Securities available-for-sale [Abstract]
Amortized Cost	474,229	477,761
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax	52	69
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax	41,850	41,362
Fair Value	432,431	436,468
Available-for-sale, Amortized Cost [Abstract]
Amortized Cost	474,229	477,761
Available-for-sale, Fair Value [Abstract]
Fair Value	432,431	436,468
Securities held-to-maturity [Abstract]
Amortized Cost	85,225	86,009
Gross Unrealized Gains	0	0
Gross Unrealized Losses	8,936	8,414
Fair Value	76,289	77,595
Held-to-maturity, Amortized Cost [Abstract]
Amortized Cost	85,225	86,009
Held-to-maturity, Fair Value [Abstract]
Fair Value	$ 76,289	$ 77,595