Loans and Allowance for Credit Losses - Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	$ 222,465	$ 87,194	$ 94,777	$ 83,575
Impact of adopting ASC 326			38,102
Charged-off loans	(9,002)	(8,480)	(20,695)	(14,548)
Recovery of previously charged-off loans	3,617	4,344	5,155	6,847
Provision for Loan and Lease Losses	68,292	7,195	168,033	14,379
Ending Balance	285,372	90,253	285,372	90,253
Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Impact of adopting ASC 326			34,300
Commercial real estate- owner occupied
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	23,634	12,618	13,406	11,297
Impact of adopting ASC 326			264
Charged-off loans	0	(1,065)	(1,061)	(1,586)
Recovery of previously charged-off loans	80	16	225	76
Provision for Loan and Lease Losses	15,089	605	25,969	2,387
Ending Balance	38,803	12,174	38,803	12,174
Commercial real estate- Non-owner occupied
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	32,114	17,549	19,963	15,649
Impact of adopting ASC 326			(4,740)
Charged-off loans	(2)	0	(263)	(13)
Recovery of previously charged-off loans	106	876	199	888
Provision for Loan and Lease Losses	36,208	227	53,267	2,128
Ending Balance	68,426	18,652	68,426	18,652
Consumer real estate – mortgage
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	32,998	8,369	8,054	7,670
Impact of adopting ASC 326			21,029
Charged-off loans	(1,196)	(580)	(2,126)	(930)
Recovery of previously charged-off loans	484	372	674	741
Provision for Loan and Lease Losses	(2,928)	328	1,727	1,008
Ending Balance	29,358	8,489	29,358	8,489
Construction and land development
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	38,911	10,915	12,662	11,128
Impact of adopting ASC 326			(3,144)
Charged-off loans	0	(4)	0	(4)
Recovery of previously charged-off loans	50	19	93	141
Provision for Loan and Lease Losses	2,936	276	32,286	(59)
Ending Balance	41,897	11,206	41,897	11,206
Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	88,060	32,699	36,112	31,731
Impact of adopting ASC 326			23,040
Charged-off loans	(6,734)	(5,408)	(14,998)	(8,760)
Recovery of previously charged-off loans	2,249	2,744	2,997	4,342
Provision for Loan and Lease Losses	17,035	7,401	53,459	10,123
Ending Balance	100,610	37,436	100,610	37,436
Consumer and other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	6,748	4,803	3,595	5,423
Impact of adopting ASC 326			2,638
Charged-off loans	(1,070)	(1,423)	(2,247)	(3,255)
Recovery of previously charged-off loans	648	317	967	659
Provision for Loan and Lease Losses	(48)	(1,583)	1,325	(713)
Ending Balance	6,278	2,114	6,278	2,114
Unallocated
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	0	241	985	677
Impact of adopting ASC 326			(985)
Charged-off loans	0	0	0	0
Recovery of previously charged-off loans	0	0	0	0
Provision for Loan and Lease Losses	0	(59)	0	(495)
Ending Balance	$ 0	$ 182	$ 0	$ 182

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Amount of increase (decrease) in allowance for credit loss on financing receivable.

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Amount of writeoff of financing receivable, charged against allowance for credit loss.

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