Investment Securities - Unrealized Losses on Securities Available-for-Sale (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 4,242,422	$ 457,559
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	40,254	2,474
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	76,794	90,077
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	513	904
Debt Securities, Available-for-sale, Unrealized Loss Position	4,319,216	547,636
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	40,767	3,378
Government agency and government-sponsored enterprise collateralized mortgage obligations
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	189,684	97,863
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3,700	280
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	11,283	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	39	0
Debt Securities, Available-for-sale, Unrealized Loss Position	200,967	97,863
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	3,739	280
Municipal securities
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	583,499	5,919
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	6,860	18
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,559	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	131	0
Debt Securities, Available-for-sale, Unrealized Loss Position	586,058	5,919
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	6,991	18
Government agency and government-sponsored enterprise commercial mortgage-backed securities
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	282,753	58,408
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	5,023	37
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	282,753	58,408
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	5,023	37
Asset-backed Securities
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	25,044	14,636
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	49	53
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	16,126	61,031
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	230	707
Debt Securities, Available-for-sale, Unrealized Loss Position	41,170	75,667
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	279	760
Collateralized loan obligations
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	202,528	96,442
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	600	729
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	43,930	28,972
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	73	195
Debt Securities, Available-for-sale, Unrealized Loss Position	246,458	125,414
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	673	924
Private label collateralized mortgage obligations
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	234,541	788
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,555	19
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	319	74
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	15	2
Debt Securities, Available-for-sale, Unrealized Loss Position	234,860	862
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	1,570	21
SBA asset-backed securities
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	0	2,127
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	27
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,897	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	17	0
Debt Securities, Available-for-sale, Unrealized Loss Position	1,897	2,127
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	17	27
Corporate debt securities
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	127,786	87,596
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,161	404
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	127,786	87,596
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	1,161	404
U.S. Treasury securities
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	632,950
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	4,099
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0
Debt Securities, Available-for-sale, Unrealized Loss Position	632,950
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	4,099	0
Private label commercial MBS
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	266,238	3,058
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,428	10
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	266,238	3,058
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	1,428	10
Agency residential MBS
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1,697,399	90,722
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	15,779	897
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	680	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	8	0
Debt Securities, Available-for-sale, Unrealized Loss Position	1,698,079	90,722
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	$ 15,787	$ 897

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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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 continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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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), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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