Allowance for Credit Losses - Activity in Allowance for Loan Losses (Details) - USD ($) $ in Thousands		3 Months Ended
Jan. 01, 2020	Mar. 31, 2020	Mar. 31, 2019
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	$ 35,154	$ 35,154	$ 32,423
Initial Allowance on PCD Loans Acquired During the Period		516
Provision for Credit Losses		29,513	1,397
Charge- Offs		(1,647)	(1,479)
Recoveries		673	516
TDR Allowance Adjustments		(24)	(35)
Ending Balance		85,411	32,822
Construction & land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	1,842	1,842	2,233
Initial Allowance on PCD Loans Acquired During the Period		48
Provision for Credit Losses		1,248	83
Charge- Offs		0	0
Recoveries		29	4
TDR Allowance Adjustments		0	0
Ending Balance		4,646	2,320
Commercial real estate - owner occupied
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	5,361	5,361
Initial Allowance on PCD Loans Acquired During the Period		207
Provision for Credit Losses		(264)
Charge- Offs		(44)
Recoveries		0
TDR Allowance Adjustments		(13)
Ending Balance		5,327
Commercial real estate - non owner occupied
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	7,863	7,863
Initial Allowance on PCD Loans Acquired During the Period		140
Provision for Credit Losses		18,283
Charge- Offs		(12)
Recoveries		28
TDR Allowance Adjustments		0
Ending Balance		35,643
Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	13,224	13,224	11,112
Provision for Credit Losses			625
Charge- Offs			(16)
Recoveries			47
TDR Allowance Adjustments			(15)
Ending Balance			11,753
Residential real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	7,667	7,667	7,775
Initial Allowance on PCD Loans Acquired During the Period		97
Provision for Credit Losses		6,260	(414)
Charge- Offs		(18)	(36)
Recoveries		116	139
TDR Allowance Adjustments		(10)	(19)
Ending Balance		19,899	7,445
Commercial and financial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	9,716	9,716	8,585
Initial Allowance on PCD Loans Acquired During the Period		11
Provision for Credit Losses		2,746	853
Charge- Offs		(1,100)	(944)
Recoveries		420	79
TDR Allowance Adjustments		0	0
Ending Balance		15,470	8,573
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	2,705	2,705	2,718
Initial Allowance on PCD Loans Acquired During the Period		13
Provision for Credit Losses		1,240	250
Charge- Offs		(473)	(483)
Recoveries		80	247
TDR Allowance Adjustments		(1)	(1)
Ending Balance		$ 4,426	$ 2,731
Cumulative Effect Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Initial Allowance on PCD Loans Acquired During the Period	700
Ending Balance	21,226
Cumulative Effect Adjustment \| Construction & land development
Allowance for Loan and Lease Losses [Roll Forward]
Ending Balance	1,479
Cumulative Effect Adjustment \| Commercial real estate - owner occupied
Allowance for Loan and Lease Losses [Roll Forward]
Ending Balance	80
Cumulative Effect Adjustment \| Commercial real estate - non owner occupied
Allowance for Loan and Lease Losses [Roll Forward]
Ending Balance	9,341
Cumulative Effect Adjustment \| Residential real estate
Allowance for Loan and Lease Losses [Roll Forward]
Ending Balance	5,787
Cumulative Effect Adjustment \| Commercial and financial
Allowance for Loan and Lease Losses [Roll Forward]
Ending Balance	3,677
Cumulative Effect Adjustment \| Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Ending Balance	$ 862

Amount of other addition (reduction) in allowance reserve for credit loss.

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Amount of increase in allowance for credit loss on financing receivable purchased with credit deterioration.

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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 recovery of financing receivables doubtful of collection that were previously charged off.

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Amount of credit loss expense (reversal of expense) for financing receivable.

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