Allowance for Loan Losses - Roll Forward Of the Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Allowance for loan losses:
Beginning balance	$ 50,059	$ 47,355	$ 49,026	$ 46,211
Charge-offs	(4,965)	(1,340)	(7,953)	(4,986)
Recoveries	4,020	345	5,641	1,575
Net (charge-offs) recoveries	(945)	(995)	(2,312)	(3,411)
Provision for loan losses charged to operations	1,700	2,250	4,100	5,810
Ending balance	50,814	48,610	50,814	48,610
Individually evaluated for impairment	2,045	1,280	2,045	1,280
Collectively evaluated for impairment	46,221	44,502	46,221	44,502
Purchased with deteriorated credit quality
Allowance for loan losses:
Ending balance	2,548	2,828	2,548	2,828
Commercial
Allowance for loan losses:
Beginning balance	9,534	7,146	8,269	5,542
Charge-offs	(757)	(511)	(1,709)	(1,627)
Recoveries	761	24	1,376	373
Net (charge-offs) recoveries	4	(487)	(333)	(1,254)
Provision for loan losses charged to operations	750	1,448	2,352	3,819
Ending balance	10,288	8,107	10,288	8,107
Individually evaluated for impairment	1,382	421	1,382	421
Collectively evaluated for impairment	8,778	7,326	8,778	7,326
Commercial | Purchased with deteriorated credit quality
Allowance for loan losses:
Ending balance	128	360	128	360
Real estate – construction
Allowance for loan losses:
Beginning balance	5,302	4,702	4,755	3,428
Charge-offs	0	0	0	0
Recoveries	0	3	7	10
Net (charge-offs) recoveries	0	3	7	10
Provision for loan losses charged to operations	(175)	8	365	1,275
Ending balance	5,127	4,713	5,127	4,713
Individually evaluated for impairment	24	70	24	70
Collectively evaluated for impairment	5,103	4,643	5,103	4,643
Real estate – construction | Purchased with deteriorated credit quality
Allowance for loan losses:
Ending balance	0	0	0	0
Real estate – 1-4 family mortgage
Allowance for loan losses:
Beginning balance	9,616	11,657	10,139	12,009
Charge-offs	(268)	(211)	(1,143)	(1,861)
Recoveries	219	119	531	335
Net (charge-offs) recoveries	(49)	(92)	(612)	(1,526)
Provision for loan losses charged to operations	282	(1,497)	322	(415)
Ending balance	9,849	10,068	9,849	10,068
Individually evaluated for impairment	186	70	186	70
Collectively evaluated for impairment	9,313	9,493	9,313	9,493
Real estate – 1-4 family mortgage | Purchased with deteriorated credit quality
Allowance for loan losses:
Ending balance	350	505	350	505
Real estate – commercial mortgage
Allowance for loan losses:
Beginning balance	24,302	22,450	24,492	23,384
Charge-offs	(677)	(216)	(1,406)	(875)
Recoveries	33	152	644	756
Net (charge-offs) recoveries	(644)	(64)	(762)	(119)
Provision for loan losses charged to operations	381	2,041	309	1,162
Ending balance	24,039	24,427	24,039	24,427
Individually evaluated for impairment	450	715	450	715
Collectively evaluated for impairment	21,521	21,751	21,521	21,751
Real estate – commercial mortgage | Purchased with deteriorated credit quality
Allowance for loan losses:
Ending balance	2,068	1,961	2,068	1,961
Installment and Other
Allowance for loan losses:
Beginning balance	1,305	1,400	1,371	1,848
Charge-offs	(3,263)	(402)	(3,695)	(623)
Recoveries	3,007	47	3,083	101
Net (charge-offs) recoveries	(256)	(355)	(612)	(522)
Provision for loan losses charged to operations	462	250	752	(31)
Ending balance	1,511	1,295	1,511	1,295
Individually evaluated for impairment	3	4	3	4
Collectively evaluated for impairment	1,506	1,289	1,506	1,289
Installment and Other | Purchased with deteriorated credit quality
Allowance for loan losses:
Ending balance	$ 2	$ 2	$ 2	$ 2