Loans and Leases - Allowance for Loan and Lease Losses (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	$ 301,050	$ 135,037	$ 138,785	$ 132,472
Charge-offs	(37,284)	(6,501)	(73,275)	(27,603)
Recoveries	1,200	2,016	4,839	11,683
Net charge-offs	(36,084)	(4,485)	(68,436)	(15,920)
Provision	81,000	8,000	272,000	22,000
Balance, end of period	345,966	138,552	345,966	138,552
Amount of the allowance applicable to loans and leases:
Individually evaluated	2,924	9,330	2,924	9,330
Collectively evaluated	343,042	129,222	343,042	129,222
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	95,135	110,620	95,135	110,620
Collectively evaluated	18,931,065	18,624,923	18,931,065	18,624,923
Loans held for investment, net	19,026,200	18,735,543	19,026,200	18,735,543	$ 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	130,724	46,826	44,575	46,021
Charge-offs	(1,551)	(120)	(6,233)	(850)
Recoveries	109	95	360	478
Net charge-offs	(1,442)	(25)	(5,873)	(372)
Provision	(7,588)	(1,655)	77,684	(503)
Balance, end of period	121,694	45,146	121,694	45,146
Amount of the allowance applicable to loans and leases:
Individually evaluated	340	248	340	248
Collectively evaluated	121,354	44,898	121,354	44,898
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	51,852	29,808	51,852	29,808
Collectively evaluated	7,825,193	7,867,116	7,825,193	7,867,116
Loans held for investment, net	7,877,045	7,896,924	7,877,045	7,896,924	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	70,113	26,378	30,544	28,209
Charge-offs	0	0	0	0
Recoveries	21	0	21	0
Net charge-offs	21	0	21	0
Provision	20,039	683	68,200	(1,148)
Balance, end of period	90,173	27,061	90,173	27,061
Amount of the allowance applicable to loans and leases:
Individually evaluated	0	0	0	0
Collectively evaluated	90,173	27,061	90,173	27,061
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	1,782	5,357	1,782	5,357
Collectively evaluated	3,421,965	2,546,117	3,421,965	2,546,117
Loans held for investment, net	3,423,747	2,551,474	3,423,747	2,551,474	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	97,947	59,401	61,528	56,360
Charge-offs	(35,666)	(6,021)	(66,337)	(25,951)
Recoveries	1,063	1,898	4,410	11,084
Net charge-offs	(34,603)	(4,123)	(61,927)	(14,867)
Provision	64,921	8,907	121,804	22,692
Balance, end of period	128,265	64,185	128,265	64,185
Amount of the allowance applicable to loans and leases:
Individually evaluated	2,584	9,082	2,584	9,082
Collectively evaluated	125,681	55,103	125,681	55,103
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	41,501	75,455	41,501	75,455
Collectively evaluated	7,321,673	7,803,102	7,321,673	7,803,102
Loans held for investment, net	7,363,174	7,878,557	7,363,174	7,878,557	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	2,266	2,432	2,138	1,882
Charge-offs	(67)	(360)	(705)	(802)
Recoveries	7	23	48	121
Net charge-offs	(60)	(337)	(657)	(681)
Provision	3,628	65	4,312	959
Balance, end of period	5,834	2,160	5,834	2,160
Amount of the allowance applicable to loans and leases:
Individually evaluated	0	0	0	0
Collectively evaluated	5,834	2,160	5,834	2,160
The ending balance of the loan and lease portfolio is composed of loans and leases:
Individually evaluated	0	0	0	0
Collectively evaluated	362,234	408,588	362,234	408,588
Loans held for investment, net	$ 362,234	$ 408,588	362,234	$ 408,588	$ 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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