Loans and Allowance for Credit Losses - Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	$ 285,372	$ 90,253	$ 94,777	$ 83,575
Impact of adopting ASC 326			38,102
Charged-off loans	(15,029)	(6,780)	(35,724)	(21,328)
Recovery of previously charged-off loans	1,973	1,914	7,128	8,761
Provision for Loan and Lease Losses	16,329	8,260	184,362	22,639
Ending Balance	288,645	93,647	288,645	93,647
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	38,803	12,174	13,406	11,297
Impact of adopting ASC 326			264
Charged-off loans	(186)	(40)	(1,247)	(1,626)
Recovery of previously charged-off loans	47	135	272	211
Provision for Loan and Lease Losses	(2,238)	(112)	23,731	2,275
Ending Balance	36,426	12,157	36,426	12,157
Commercial real estate- Non-owner occupied
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	68,426	18,652	19,963	15,649
Impact of adopting ASC 326			(4,740)
Charged-off loans	(222)	(62)	(485)	(75)
Recovery of previously charged-off loans	432	74	631	962
Provision for Loan and Lease Losses	1,223	1,796	54,490	3,924
Ending Balance	69,859	20,460	69,859	20,460
Consumer real estate – mortgage
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	29,358	8,489	8,054	7,670
Impact of adopting ASC 326			21,029
Charged-off loans	(907)	(194)	(3,033)	(1,124)
Recovery of previously charged-off loans	297	901	971	1,642
Provision for Loan and Lease Losses	3,201	(1,426)	4,928	(418)
Ending Balance	31,949	7,770	31,949	7,770
Construction and land development
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	41,897	11,206	12,662	11,128
Impact of adopting ASC 326			(3,144)
Charged-off loans	0	(14)	0	(18)
Recovery of previously charged-off loans	7	97	100	238
Provision for Loan and Lease Losses	(682)	585	31,604	526
Ending Balance	41,222	11,874	41,222	11,874
Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	100,610	37,436	36,112	31,731
Impact of adopting ASC 326			23,040
Charged-off loans	(12,984)	(5,082)	(27,982)	(13,842)
Recovery of previously charged-off loans	799	407	3,798	4,749
Provision for Loan and Lease Losses	13,783	1,814	67,240	11,937
Ending Balance	102,208	34,575	102,208	34,575
Consumer and other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	6,278	2,114	3,595	5,423
Impact of adopting ASC 326			2,638
Charged-off loans	(730)	(1,388)	(2,977)	(4,643)
Recovery of previously charged-off loans	391	300	1,356	959
Provision for Loan and Lease Losses	1,042	3,278	2,369	2,565
Ending Balance	6,981	4,304	6,981	4,304
Unallocated
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	0	182	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	2,325	0	1,830
Ending Balance	$ 0	$ 2,507	$ 0	$ 2,507

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

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