Loans and Leases - Allowance for Loan and Lease Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	$ 225,600	$ 301,050	$ 348,181	$ 138,785
Charge-offs	(1,516)	(37,284)	(6,320)	(73,275)
Recoveries	1,149	1,200	8,372	4,839
Net (charge-offs) recoveries	(367)	(36,084)	2,052	(68,436)
Provision	(21,500)	81,000	(146,500)	272,000
Balance, end of period	203,733	345,966	203,733	345,966
Amount of the allowance applicable to loans and leases:
Individually evaluated	2,910	2,924	2,910	2,924
Collectively evaluated	200,823	343,042	200,823	343,042
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	92,833	95,135	92,833	95,135
Collectively evaluated	20,418,187	18,931,065	20,418,187	18,931,065
Loans held for investment, net	20,511,020	19,026,200	20,511,020	19,026,200	$ 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	107,013	130,724	138,342	44,575
Charge-offs	(29)	(1,551)	(663)	(6,233)
Recoveries	563	109	5,990	360
Net (charge-offs) recoveries	534	(1,442)	5,327	(5,873)
Provision	(11,344)	(7,588)	(47,466)	77,684
Balance, end of period	96,203	121,694	96,203	121,694
Amount of the allowance applicable to loans and leases:
Individually evaluated	189	340	189	340
Collectively evaluated	96,014	121,354	96,014	121,354
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	34,822	51,852	34,822	51,852
Collectively evaluated	9,546,135	7,825,193	9,546,135	7,825,193
Loans held for investment, net	9,580,957	7,877,045	9,580,957	7,877,045	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	54,582	70,113	78,356	30,544
Charge-offs	0	0	(775)	0
Recoveries	0	21	0	21
Net (charge-offs) recoveries	0	21	(775)	21
Provision	(1,923)	20,039	(24,922)	68,200
Balance, end of period	52,659	90,173	52,659	90,173
Amount of the allowance applicable to loans and leases:
Individually evaluated	0	0	0	0
Collectively evaluated	52,659	90,173	52,659	90,173
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	19,364	1,782	19,364	1,782
Collectively evaluated	3,632,509	3,421,965	3,632,509	3,421,965
Loans held for investment, net	3,651,873	3,423,747	3,651,873	3,423,747	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	57,697	97,947	126,403	61,528
Charge-offs	(951)	(35,666)	(3,802)	(66,337)
Recoveries	543	1,063	2,269	4,410
Net (charge-offs) recoveries	(408)	(34,603)	(1,533)	(61,927)
Provision	(9,792)	64,921	(77,373)	121,804
Balance, end of period	47,497	128,265	47,497	128,265
Amount of the allowance applicable to loans and leases:
Individually evaluated	2,721	2,584	2,721	2,584
Collectively evaluated	44,776	125,681	44,776	125,681
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	38,647	41,501	38,647	41,501
Collectively evaluated	6,833,575	7,321,673	6,833,575	7,321,673
Loans held for investment, net	6,872,222	7,363,174	6,872,222	7,363,174	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	6,308	2,266	5,080	2,138
Charge-offs	(536)	(67)	(1,080)	(705)
Recoveries	43	7	113	48
Net (charge-offs) recoveries	(493)	(60)	(967)	(657)
Provision	1,559	3,628	3,261	4,312
Balance, end of period	7,374	5,834	7,374	5,834
Amount of the allowance applicable to loans and leases:
Individually evaluated	0	0	0	0
Collectively evaluated	7,374	5,834	7,374	5,834
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	0	0	0	0
Collectively evaluated	405,968	362,234	405,968	362,234
Loans held for investment, net	$ 405,968	362,234	$ 405,968	362,234	$ 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)