Allowance for Credit Losses - Activity in Allowance for Credit Losses (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Jan. 01, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	$ 35,154	$ 91,250	$ 33,505	$ 35,154	$ 32,423
Initial Allowance on PCD Loans Acquired During the Period		5,763		6,279
Provision for credit losses		(1,245)	2,251	35,879	6,199
Charge- Offs		(2,175)	(2,592)	(6,316)	(6,715)
Recoveries		439	481	1,856	1,800
TDR Allowance Adjustments		(19)	(40)	(65)	(102)
Ending Balance		94,013	33,605	$ 94,013	33,605
Provision for credit losses on accrued interest receivable		400
Accounting Standards Update [Extensible List]				us-gaap:AccountingStandardsUpdate201613Member
Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	1,842	7,161	2,243	$ 1,842	2,233
Initial Allowance on PCD Loans Acquired During the Period		39		87
Provision for credit losses		475	(395)	4,202	(391)
Charge- Offs		0	0	0	0
Recoveries		26	6	92	13
TDR Allowance Adjustments		0	0	(1)	(1)
Ending Balance		7,701	1,854	7,701	1,854
Commercial real estate - owner-occupied
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	5,361	5,562		5,361
Initial Allowance on PCD Loans Acquired During the Period		954		1,161
Provision for credit losses		689		655
Charge- Offs		0		(45)
Recoveries		26		44
TDR Allowance Adjustments		(12)		(37)
Ending Balance		7,219		7,219
Commercial real estate - non owner-occupied
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	7,863	38,992		7,863
Initial Allowance on PCD Loans Acquired During the Period		2,096		2,236
Provision for credit losses		(7,050)		14,578
Charge- Offs		(25)		(37)
Recoveries		5		37
TDR Allowance Adjustments		0		0
Ending Balance		34,018		34,018
Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	13,224		11,870	13,224	11,112
Provision for credit losses			1,368		1,560
Charge- Offs			(232)		(248)
Recoveries			10		622
TDR Allowance Adjustments			(19)		(49)
Ending Balance			12,997		12,997
Residential real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	7,667	20,453	7,508	7,667	7,775
Initial Allowance on PCD Loans Acquired During the Period		27		124
Provision for credit losses		(3,196)	87	3,638	(276)
Charge- Offs		(19)	(38)	(150)	(102)
Recoveries		65	52	283	242
TDR Allowance Adjustments		(5)	(20)	(24)	(50)
Ending Balance		17,325	7,589	17,325	7,589
Commercial and financial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	9,716	15,514	8,912	9,716	8,585
Initial Allowance on PCD Loans Acquired During the Period		2,632		2,643
Provision for credit losses		8,081	769	12,144	3,736
Charge- Offs		(1,776)	(1,625)	(4,642)	(4,450)
Recoveries		203	295	1,116	480
TDR Allowance Adjustments		0	0	0	0
Ending Balance		24,654	8,351	24,654	8,351
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	2,705	3,568	2,972	2,705	2,718
Initial Allowance on PCD Loans Acquired During the Period		15		28
Provision for credit losses		(244)	422	662	1,570
Charge- Offs		(355)	(697)	(1,442)	(1,915)
Recoveries		114	118	284	443
TDR Allowance Adjustments		(2)	(1)	(3)	(2)
Ending Balance		3,096	$ 2,814	3,096	$ 2,814
Paycheck Protection Program
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	0	0		0
Initial Allowance on PCD Loans Acquired During the Period		0		0
Provision for credit losses		0		0
Charge- Offs		0		0
Recoveries		0		0
TDR Allowance Adjustments		0		0
Ending Balance		$ 0		0
Cumulative Effect Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	21,226			21,226
Initial Allowance on PCD Loans Acquired During the Period	700
Ending Balance	21,226
Cumulative Effect Adjustment | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	1,479			1,479
Cumulative Effect Adjustment | Commercial real estate - owner-occupied
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	80			80
Cumulative Effect Adjustment | Commercial real estate - non owner-occupied
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	9,341			9,341
Cumulative Effect Adjustment | Residential real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	5,787			5,787
Cumulative Effect Adjustment | Commercial and financial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	3,677			3,677
Cumulative Effect Adjustment | Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	862			862
Cumulative Effect Adjustment | Paycheck Protection Program
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	$ 0			$ 0