Loans and Allowance - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
Loans held for sale	$ 4,778				$ 7,216				$ 4,778	$ 7,216
Allowance for loan losses	80,552				75,032				80,552	75,032	$ 66,037	$ 62,453
Increase in allowance for loan losses									5,520
Net charge offs									1,707
Increase in net charge offs									1,559
Provision for loan losses	1,664	$ 1,400	$ 1,663	$ 2,500	1,800	$ 2,083	$ 2,875	$ 2,385	7,227	9,143	5,657
Increase in provision for loan losses									1,916
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	7,224,467				6,751,199				7,224,467	6,751,199
Loans acquired with deteriorated credit quality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	15,784				24,954				15,784	24,954
Commercial and consumer loan | Loans acquired with deteriorated credit quality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,541				315				$ 1,541	315
Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of troubled debt restructured loans									79.00%
Residential
Receivables [Abstract]
Allowance for loan losses	14,322				13,537				$ 14,322	13,537	11,755	$ 11,139
Provision for loan losses									1,969	2,391	$ 1,515
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,494,578				1,476,786				1,494,578	1,476,786
Mortgage loans for which formal foreclosure proceedings are in process	800				2,302				800	2,302
Residential | Loans acquired with deteriorated credit quality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 1,293				$ 1,536				$ 1,293	$ 1,536