Loans and Leases - Allowance for Loan and Lease Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	$ 292,445	$ 221,292	$ 348,181	$ 138,785
Charge-offs	(816)	(15,786)	(4,804)	(35,991)
Recoveries	5,971	2,544	7,223	3,639
Net (charge-offs) recoveries	5,155	(13,242)	2,419	(32,352)
Provision	(72,000)	93,000	(125,000)	191,000
Balance, end of period	225,600	301,050	225,600	301,050
Amount of the allowance applicable to loans and leases:
Individually evaluated	3,468	8,493	3,468	8,493
Collectively evaluated	222,132	292,557	222,132	292,557
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	90,799	175,700	90,799	175,700
Collectively evaluated	19,415,458	19,518,931	19,415,458	19,518,931
Loans held for investment, net	19,506,257	19,694,631	19,506,257	19,694,631	$ 19,083,377
Cumulative Effect of Change in Accounting Principle - CECL
Allowance for Loan and Lease Losses [Roll Forward]
Balance, end of period		(3,617)		(3,617)
Real Estate Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	141,122	91,372	138,342	44,575
Charge-offs	(266)	(4,182)	(634)	(4,682)
Recoveries	4,882	127	5,427	251
Net (charge-offs) recoveries	4,616	(4,055)	4,793	(4,431)
Provision	(38,725)	43,407	(36,122)	85,272
Balance, end of period	107,013	130,724	107,013	130,724
Amount of the allowance applicable to loans and leases:
Individually evaluated	203	211	203	211
Collectively evaluated	106,810	130,513	106,810	130,513
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	41,145	68,240	41,145	68,240
Collectively evaluated	8,371,875	7,887,494	8,371,875	7,887,494
Loans held for investment, net	8,413,020	7,955,734	8,413,020	7,955,734	7,899,936
Real Estate Mortgage | Cumulative Effect of Change in Accounting Principle - CECL
Allowance for Loan and Lease Losses [Roll Forward]
Balance, end of period		(5,308)		(5,308)
Real Estate Construction and Land
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	66,775	40,173	78,356	30,544
Charge-offs	(75)	0	(775)	0
Recoveries	0	0	0	0
Net (charge-offs) recoveries	(75)	0	(775)	0
Provision	(12,118)	29,940	(22,999)	48,161
Balance, end of period	54,582	70,113	54,582	70,113
Amount of the allowance applicable to loans and leases:
Individually evaluated	0	0	0	0
Collectively evaluated	54,582	70,113	54,582	70,113
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	3,254	1,799	3,254	1,799
Collectively evaluated	3,502,330	3,338,729	3,502,330	3,338,729
Loans held for investment, net	3,505,584	3,340,528	3,505,584	3,340,528	3,360,281
Real Estate Construction and Land | Cumulative Effect of Change in Accounting Principle - CECL
Allowance for Loan and Lease Losses [Roll Forward]
Balance, end of period		8,592		8,592
Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	78,716	87,570	126,403	61,528
Charge-offs	(277)	(11,439)	(2,851)	(30,671)
Recoveries	1,029	2,392	1,726	3,347
Net (charge-offs) recoveries	752	(9,047)	(1,125)	(27,324)
Provision	(21,771)	19,424	(67,581)	56,883
Balance, end of period	57,697	97,947	57,697	97,947
Amount of the allowance applicable to loans and leases:
Individually evaluated	3,265	8,282	3,265	8,282
Collectively evaluated	54,432	89,665	54,432	89,665
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	46,400	105,661	46,400	105,661
Collectively evaluated	7,175,844	7,881,389	7,175,844	7,881,389
Loans held for investment, net	7,222,244	7,987,050	7,222,244	7,987,050	7,502,905
Commercial | Cumulative Effect of Change in Accounting Principle - CECL
Allowance for Loan and Lease Losses [Roll Forward]
Balance, end of period		(6,860)		(6,860)
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	5,832	2,177	5,080	2,138
Charge-offs	(198)	(165)	(544)	(638)
Recoveries	60	25	70	41
Net (charge-offs) recoveries	(138)	(140)	(474)	(597)
Provision	614	229	1,702	684
Balance, end of period	6,308	2,266	6,308	2,266
Amount of the allowance applicable to loans and leases:
Individually evaluated	0	0	0	0
Collectively evaluated	6,308	2,266	6,308	2,266
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	0	0	0	0
Collectively evaluated	365,409	411,319	365,409	411,319
Loans held for investment, net	$ 365,409	411,319	$ 365,409	411,319	$ 320,255
Consumer | Cumulative Effect of Change in Accounting Principle - CECL
Allowance for Loan and Lease Losses [Roll Forward]
Balance, end of period		$ (41)		$ (41)