Allowance for Loan Losses - Changes in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Rollforward of the allowance for loan losses
Beginning balance				$ 49,026				$ 46,211	$ 49,026	$ 46,211	$ 42,737
Charge-offs									(13,478)	(6,428)	(7,008)
Recoveries									9,564	2,433	2,932
Net charge-offs									(3,914)	(3,995)	(4,076)
Provision for loan losses											7,550
Provision for loan losses	$ 2,950	$ 1,700	$ 900	1,500	$ 1,000	$ 2,250	$ 1,810	1,750	7,050	6,810	7,550
Ending balance	52,162				49,026				52,162	49,026	46,211
Period-End Amount Allocated to:
Individually evaluated for impairment												$ 2,012	$ 1,514	$ 2,674
Collectively evaluated for impairment												48,179	44,960	41,760
Purchased with deteriorated credit quality	52,162			49,026	49,026			46,211	52,162	46,211	46,211	52,162	49,026	46,211
Receivables Acquired with Deteriorated Credit Quality
Rollforward of the allowance for loan losses
Beginning balance				2,552				1,777	2,552	1,777
Ending balance	1,971				2,552				1,971	2,552	1,777
Period-End Amount Allocated to:
Purchased with deteriorated credit quality	1,971			2,552	2,552			1,777	2,552	1,777	1,777	1,971	2,552	1,777
Commercial, financial, agricultural
Rollforward of the allowance for loan losses
Beginning balance				8,269				5,542	8,269	5,542	5,486
Charge-offs									(2,681)	(2,415)	(2,874)
Recoveries									1,428	618	422
Net charge-offs									(1,253)	(1,797)	(2,452)
Provision for loan losses											2,508
Provision for loan losses									3,642	4,524
Ending balance	10,658				8,269				10,658	8,269	5,542
Period-End Amount Allocated to:
Individually evaluated for impairment												1,434	336	190
Collectively evaluated for impairment												8,932	7,772	5,040
Purchased with deteriorated credit quality	10,658			8,269	8,269			5,542	8,269	5,542	5,542	10,658	8,269	5,542
Commercial, financial, agricultural | Receivables Acquired with Deteriorated Credit Quality
Rollforward of the allowance for loan losses
Beginning balance				161				312	161	312
Ending balance	292				161				292	161	312
Period-End Amount Allocated to:
Purchased with deteriorated credit quality	292			161	161			312	161	312	312	292	161	312
Real estate – construction
Rollforward of the allowance for loan losses
Beginning balance				4,755				3,428	4,755	3,428	2,380
Charge-offs									0	(51)	0
Recoveries									21	13	105
Net charge-offs									21	(38)	105
Provision for loan losses											943
Provision for loan losses									253	1,365
Ending balance	5,029				4,755				5,029	4,755	3,428
Period-End Amount Allocated to:
Individually evaluated for impairment												16	68	4
Collectively evaluated for impairment												5,013	4,687	3,424
Purchased with deteriorated credit quality	5,029			4,755	4,755			3,428	4,755	3,428	3,428	5,029	4,755	3,428
Real estate – construction | Receivables Acquired with Deteriorated Credit Quality
Rollforward of the allowance for loan losses
Beginning balance				0				0	0	0
Ending balance	0				0				0	0	0
Period-End Amount Allocated to:
Purchased with deteriorated credit quality	0			0	0			0	0	0	0	0	0	0
Real estate – 1-4 family mortgage
Rollforward of the allowance for loan losses
Beginning balance				10,139				12,009	10,139	12,009	14,294
Charge-offs									(1,602)	(2,023)	(1,713)
Recoveries									712	573	733
Net charge-offs									(890)	(1,450)	(980)
Provision for loan losses											(1,305)
Provision for loan losses									565	(420)
Ending balance	9,814				10,139				9,814	10,139	12,009
Period-End Amount Allocated to:
Individually evaluated for impairment												160	79	606
Collectively evaluated for impairment												9,363	9,572	10,831
Purchased with deteriorated credit quality	9,814			10,139	10,139			12,009	9,814	12,009	14,294	9,814	10,139	12,009
Real estate – 1-4 family mortgage | Receivables Acquired with Deteriorated Credit Quality
Rollforward of the allowance for loan losses
Beginning balance				488				572	488	572
Ending balance	291				488				291	488	572
Period-End Amount Allocated to:
Purchased with deteriorated credit quality	291			488	488			572	488	572	572	291	488	572
Real estate – commercial mortgage
Rollforward of the allowance for loan losses
Beginning balance				24,492				23,384	24,492	23,384	19,059
Charge-offs									(1,490)	(1,197)	(1,791)
Recoveries									689	1,108	1,565
Net charge-offs									(801)	(89)	(226)
Provision for loan losses											4,551
Provision for loan losses									1,299	1,197
Ending balance	24,990				24,492				24,990	24,492	23,384
Period-End Amount Allocated to:
Individually evaluated for impairment												396	1,027	1,867
Collectively evaluated for impairment												23,208	21,564	20,625
Purchased with deteriorated credit quality	24,990			24,492	24,492			23,384	24,492	23,384	23,384	24,990	24,492	23,384
Real estate – commercial mortgage | Receivables Acquired with Deteriorated Credit Quality
Rollforward of the allowance for loan losses
Beginning balance				1,901				892	1,901	892
Ending balance	1,386				1,901				1,386	1,901	892
Period-End Amount Allocated to:
Purchased with deteriorated credit quality	1,386			1,901	1,901			892	1,901	892	892	1,386	1,901	892
Installment and Other
Rollforward of the allowance for loan losses
Beginning balance				1,371				1,848	1,371	1,848	1,518
Charge-offs									(7,705)	(742)	(630)
Recoveries									6,714	121	107
Net charge-offs									(991)	(621)	(523)
Provision for loan losses											853
Provision for loan losses									1,291	144
Ending balance	1,671				1,371				1,671	1,371	1,848
Period-End Amount Allocated to:
Individually evaluated for impairment												6	4	7
Collectively evaluated for impairment												1,663	1,365	1,840
Purchased with deteriorated credit quality	1,671			1,371	1,371			1,848	1,371	1,848	1,848	1,671	1,371	1,848
Installment and Other | Receivables Acquired with Deteriorated Credit Quality
Rollforward of the allowance for loan losses
Beginning balance				2				1	2	1
Ending balance	2				2				2	2	1
Period-End Amount Allocated to:
Purchased with deteriorated credit quality	$ 2			$ 2	$ 2			$ 1	$ 2	$ 1	$ 1	$ 2	$ 2	$ 1