Investment Securities - Unrealized Losses on Securities Available-for-Sale (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	$ 1,430,739	$ 457,559
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(13,060)	(2,474)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	65,656	90,077
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(549)	(904)
Unrealized Losses on Securities Available-for-Sale, Fair Value	1,496,395	547,636
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(13,609)	(3,378)
Government agency and government-sponsored enterprise pass through securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	126,899	90,722
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(2,170)	(897)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	0	0
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	0	0
Unrealized Losses on Securities Available-for-Sale, Fair Value	126,899	90,722
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(2,170)	(897)
Government agency and government-sponsored enterprise collateralized mortgage obligations
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	125,880	97,863
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(2,925)	(280)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	0	0
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	0	0
Unrealized Losses on Securities Available-for-Sale, Fair Value	125,880	97,863
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(2,925)	(280)
Municipal securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	203,261	5,919
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(2,045)	(18)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	0	0
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	0	0
Unrealized Losses on Securities Available-for-Sale, Fair Value	203,261	5,919
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(2,045)	(18)
Government agency and government-sponsored enterprise commercial mortgage-backed securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	303,546	58,408
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(3,551)	(37)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	687	0
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(8)	0
Unrealized Losses on Securities Available-for-Sale, Fair Value	304,233	58,408
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(3,559)	(37)
Asset-backed Securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	0	14,636
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	0	(53)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	16,381	61,031
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(343)	(707)
Unrealized Losses on Securities Available-for-Sale, Fair Value	16,381	75,667
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(343)	(760)
Collateralized loan obligations
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	201,170	96,442
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(995)	(729)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	43,854	28,972
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(157)	(195)
Unrealized Losses on Securities Available-for-Sale, Fair Value	245,024	125,414
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(1,152)	(924)
Private label collateralized mortgage obligations
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	24,957	788
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(216)	(19)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	624	74
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(14)	(2)
Unrealized Losses on Securities Available-for-Sale, Fair Value	25,581	862
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(230)	(21)
SBA asset-backed securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	0	2,127
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	0	(27)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	1,914	0
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(19)	0
Unrealized Losses on Securities Available-for-Sale, Fair Value	1,914	2,127
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(19)	(27)
Corporate debt securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	57,401	87,596
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(498)	(404)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	0	0
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	0	0
Unrealized Losses on Securities Available-for-Sale, Fair Value	57,401	87,596
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(498)	(404)
U.S. Treasury securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	374,149
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(593)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	0
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	0
Unrealized Losses on Securities Available-for-Sale, Fair Value	374,149
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(593)
Private label commercial MBS
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	13,476	3,058
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(67)	(10)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	2,196	0
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(8)	0
Unrealized Losses on Securities Available-for-Sale, Fair Value	15,672	3,058
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	$ (75)	$ (10)