Loans and Leases - Allowance for Loan and Lease Losses (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	$ 221,292	$ 136,281	$ 138,785	$ 132,472
Charge-offs	(15,786)	(17,637)	(35,991)	(21,102)
Recoveries	2,544	6,393	3,639	9,667
Net charge-offs	(13,242)	(11,244)	(32,352)	(11,435)
Provision	93,000	10,000	191,000	14,000
Balance, end of period	301,050	135,037	301,050	135,037
Amount of the allowance applicable to loans and leases:
Individually evaluated	8,493	4,742	8,493	4,742
Collectively evaluated	292,557	130,295	292,557	130,295
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	175,700	93,350	175,700	93,350
Collectively evaluated	19,518,931	18,379,502	19,518,931	18,379,502
Loans held for investment, net	19,694,631	18,472,852	19,694,631	18,472,852	$ 18,846,872
Financing Receivable, Allowance for Loan and Lease Losses, Effect of Change in Method			3,617
Real Estate Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	91,372	45,754	44,575	46,021
Charge-offs	(4,182)	(534)	(4,682)	(730)
Recoveries	127	240	251	383
Net charge-offs	(4,055)	(294)	(4,431)	(347)
Provision	43,407	1,366	85,272	1,152
Balance, end of period	130,724	46,826	130,724	46,826
Amount of the allowance applicable to loans and leases:
Individually evaluated	211	260	211	260
Collectively evaluated	130,513	46,566	130,513	46,566
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	68,240	27,594	68,240	27,594
Collectively evaluated	7,887,494	8,048,432	7,887,494	8,048,432
Loans held for investment, net	7,955,734	8,076,026	7,955,734	8,076,026	7,972,747
Financing Receivable, Allowance for Loan and Lease Losses, Effect of Change in Method			5,308
Real Estate Construction and Land
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	40,173	27,208	30,544	28,209
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Net charge-offs	0	0	0	0
Provision	29,940	(830)	48,161	(1,831)
Balance, end of period	70,113	26,378	70,113	26,378
Amount of the allowance applicable to loans and leases:
Individually evaluated	0	0	0	0
Collectively evaluated	70,113	26,378	70,113	26,378
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	1,799	5,376	1,799	5,376
Collectively evaluated	3,338,729	2,370,754	3,338,729	2,370,754
Loans held for investment, net	3,340,528	2,376,130	3,340,528	2,376,130	2,737,802
Financing Receivable, Allowance for Loan and Lease Losses, Effect of Change in Method			(8,592)
Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	87,570	61,496	61,528	56,360
Charge-offs	(11,439)	(16,927)	(30,671)	(19,930)
Recoveries	2,392	6,080	3,347	9,186
Net charge-offs	(9,047)	(10,847)	(27,324)	(10,744)
Provision	19,424	8,752	56,883	13,785
Balance, end of period	97,947	59,401	97,947	59,401
Amount of the allowance applicable to loans and leases:
Individually evaluated	8,282	4,482	8,282	4,482
Collectively evaluated	89,665	54,919	89,665	54,919
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	105,661	60,380	105,661	60,380
Collectively evaluated	7,881,389	7,513,934	7,881,389	7,513,934
Loans held for investment, net	7,987,050	7,574,314	7,987,050	7,574,314	7,695,496
Financing Receivable, Allowance for Loan and Lease Losses, Effect of Change in Method			6,860
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	2,177	1,823	2,138	1,882
Charge-offs	(165)	(176)	(638)	(442)
Recoveries	25	73	41	98
Net charge-offs	(140)	(103)	(597)	(344)
Provision	229	712	684	894
Balance, end of period	2,266	2,432	2,266	2,432
Amount of the allowance applicable to loans and leases:
Individually evaluated	0	0	0	0
Collectively evaluated	2,266	2,432	2,266	2,432
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	0	0	0	0
Collectively evaluated	411,319	446,382	411,319	446,382
Loans held for investment, net	$ 411,319	$ 446,382	411,319	$ 446,382	$ 440,827
Financing Receivable, Allowance for Loan and Lease Losses, Effect of Change in Method			$ 41

Financing Receivable, Allowance for Credit Loss, Additional Information, Portfolio Composition [Abstract]

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Financing Receivable, Allowance for Loan and Lease Losses, Effect of Change in Method

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Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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Amount, after recoveries, of loans and leases that have been written-off.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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Amount of expense related to estimated loss from loan and lease transactions.

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