Investment Securities - Securities Available for Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss	$ 547,133	$ 72,095
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	28,143	163,035
Debt Securities, Available-for-sale	9,975,109	10,694,458
Total securities available-for-sale	10,494,099	10,603,518
Government agency and government-sponsored enterprise collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss	23,685	5,870
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2,181	22,288
Debt Securities, Available-for-sale	940,714	1,038,134
Total securities available-for-sale	962,218	1,021,716
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss	124,454	7,973
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	15,158	75,192
Debt Securities, Available-for-sale	2,125,161	2,315,968
Total securities available-for-sale	2,234,457	2,248,749
Agency residential MBS
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss	196,703	32,649
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3,461	8,866
Debt Securities, Available-for-sale	2,788,814	2,898,210
Total securities available-for-sale	2,982,056	2,921,993
Private label commercial MBS
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss	38,617	3,244
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	147
Debt Securities, Available-for-sale	401,292	450,217
Total securities available-for-sale	439,909	453,314
Asset-backed Securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss	373	324
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	375	484
Debt Securities, Available-for-sale	112,877	129,547
Total securities available-for-sale	112,875	129,387
Collateralized loan obligations
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss	1,785	444
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	236	396
Debt Securities, Available-for-sale	363,806	385,362
Total securities available-for-sale	365,355	385,410
Private label collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss	18,202	3,291
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	88	1,857
Debt Securities, Available-for-sale	238,160	264,417
Total securities available-for-sale	256,274	265,851
SBA asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss	606	32
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	726
Debt Securities, Available-for-sale	25,049	29,644
Total securities available-for-sale	25,655	28,950
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss	7,444	757
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2,619	13,774
Debt Securities, Available-for-sale	509,156	527,094
Total securities available-for-sale	513,981	514,077
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss	66,117	8,298
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	57	1,641
Debt Securities, Available-for-sale	907,743	966,898
Total securities available-for-sale	973,803	973,555
Government agency and government-sponsored enterprise commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss	69,147	9,213
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3,968	37,664
Debt Securities, Available-for-sale	1,562,337	1,688,967
Total securities available-for-sale	$ 1,627,516	$ 1,660,516

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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