Allowance for Loan Losses - Roll Forward Of the Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Allowance for loan losses:
Beginning balance	$ 49,835	$ 46,401	$ 49,026	$ 46,211
Charge-offs	(1,451)	(1,581)	(2,988)	(3,646)
Recoveries	775	725	1,621	1,230
Net (charge-offs) recoveries	(676)	(856)	(1,367)	(2,416)
Provision for loan losses charged to operations	900	1,810	2,400	3,560
Ending balance	50,059	47,355	50,059	47,355
Individually evaluated for impairment	1,873	1,515	1,873	1,515
Collectively evaluated for impairment	45,520	43,584	45,520	43,584
Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses:
Ending balance	2,666	2,256	2,666	2,256
Commercial, financial, agricultural
Allowance for loan losses:
Beginning balance	9,622	7,071	8,269	5,542
Charge-offs	(694)	(457)	(952)	(1,116)
Recoveries	241	114	615	349
Net (charge-offs) recoveries	(453)	(343)	(337)	(767)
Provision for loan losses charged to operations	365	418	1,602	2,371
Ending balance	9,534	7,146	9,534	7,146
Individually evaluated for impairment	1,191	417	1,191	417
Collectively evaluated for impairment	8,172	6,404	8,172	6,404
Commercial, financial, agricultural | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses:
Ending balance	171	325	171	325
Real estate – construction
Allowance for loan losses:
Beginning balance	4,778	4,198	4,755	3,428
Charge-offs	0	0	0	0
Recoveries	0	3	7	7
Net (charge-offs) recoveries	0	3	7	7
Provision for loan losses charged to operations	524	501	540	1,267
Ending balance	5,302	4,702	5,302	4,702
Individually evaluated for impairment	8	0	8	0
Collectively evaluated for impairment	5,294	4,702	5,294	4,702
Real estate – construction | Receivables Acquired 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	9,491	11,404	10,139	12,009
Charge-offs	(378)	(979)	(875)	(1,650)
Recoveries	115	83	312	216
Net (charge-offs) recoveries	(263)	(896)	(563)	(1,434)
Provision for loan losses charged to operations	388	1,149	40	1,082
Ending balance	9,616	11,657	9,616	11,657
Individually evaluated for impairment	188	76	188	76
Collectively evaluated for impairment	8,913	11,053	8,913	11,053
Real estate – 1-4 family mortgage | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses:
Ending balance	515	528	515	528
Real estate – commercial mortgage
Allowance for loan losses:
Beginning balance	24,643	21,914	24,492	23,384
Charge-offs	(167)	(46)	(729)	(659)
Recoveries	366	496	611	604
Net (charge-offs) recoveries	199	450	(118)	(55)
Provision for loan losses charged to operations	(540)	86	(72)	(879)
Ending balance	24,302	22,450	24,302	22,450
Individually evaluated for impairment	482	1,014	482	1,014
Collectively evaluated for impairment	21,842	20,036	21,842	20,036
Real estate – commercial mortgage | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses:
Ending balance	1,978	1,400	1,978	1,400
Installment loans to individuals
Allowance for loan losses:
Beginning balance	1,301	1,814	1,371	1,848
Charge-offs	(212)	(99)	(432)	(221)
Recoveries	53	29	76	54
Net (charge-offs) recoveries	(159)	(70)	(356)	(167)
Provision for loan losses charged to operations	163	(344)	290	(281)
Ending balance	1,305	1,400	1,305	1,400
Individually evaluated for impairment	4	8	4	8
Collectively evaluated for impairment	1,299	1,389	1,299	1,389
Installment loans to individuals | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses:
Ending balance	$ 2	$ 3	$ 2	$ 3