Purchased Loans - Impaired Loans and Average Recorded Investment and Interest Income Recognized (Details) - Purchased - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Impaired loans
Unpaid Contractual Principal Balance	$ 7,601		$ 7,601		$ 9,203
Recorded Investment With Allowance	3,262		3,262		2,892
Recorded Investment With No Allowance	3,649		3,649		5,672
Total Recorded Investment	6,911		6,911		8,564
Related Allowance	169		169		107
Average Recorded Investment	7,423	$ 7,482	7,550	$ 7,378
Interest Income Recognized	49	117	160	199
Receivables Acquired with Deteriorated Credit Quality
Impaired loans
Unpaid Contractual Principal Balance	286,613		286,613		277,709
Recorded Investment With Allowance	82,173		82,173		87,484
Recorded Investment With No Allowance	149,890		149,890		139,776
Total Recorded Investment	232,063		232,063		227,260
Related Allowance	2,828		2,828		1,777
Average Recorded Investment	207,050	258,209	211,356	261,367
Interest Income Recognized	2,506	3,911	8,184	10,230
Commercial, financial, agricultural
Impaired loans
Unpaid Contractual Principal Balance	391		391		757
Recorded Investment With Allowance	327		327		625
Recorded Investment With No Allowance	2		2		74
Total Recorded Investment	329		329		699
Related Allowance	44		44		52
Average Recorded Investment	331	413	334	332
Interest Income Recognized	3	6	8	9
Commercial, financial, agricultural \| Receivables Acquired with Deteriorated Credit Quality
Impaired loans
Unpaid Contractual Principal Balance	43,724		43,724		24,179
Recorded Investment With Allowance	4,680		4,680		5,768
Recorded Investment With No Allowance	27,959		27,959		9,547
Total Recorded Investment	32,639		32,639		15,315
Related Allowance	360		360		312
Average Recorded Investment	11,705	14,201	12,117	13,530
Interest Income Recognized	162	507	579	988
Real estate – construction
Impaired loans
Unpaid Contractual Principal Balance	520		520		1,207
Recorded Investment With Allowance	520		520		0
Recorded Investment With No Allowance	0		0		1,199
Total Recorded Investment	520		520		1,199
Related Allowance	5		5		0
Average Recorded Investment	520	829	520	741
Interest Income Recognized	1	62	2	62
Real estate – 1-4 family mortgage
Impaired loans
Unpaid Contractual Principal Balance	4,924		4,924		6,173
Recorded Investment With Allowance	834		834		1,385
Recorded Investment With No Allowance	3,495		3,495		4,225
Total Recorded Investment	4,329		4,329		5,610
Related Allowance	12		12		45
Average Recorded Investment	4,817	5,174	4,907	5,221
Interest Income Recognized	33	41	107	103
Real estate – 1-4 family mortgage \| Receivables Acquired with Deteriorated Credit Quality
Impaired loans
Unpaid Contractual Principal Balance	62,126		62,126		65,049
Recorded Investment With Allowance	13,469		13,469		15,910
Recorded Investment With No Allowance	35,724		35,724		38,059
Total Recorded Investment	49,193		49,193		53,969
Related Allowance	505		505		572
Average Recorded Investment	51,957	67,802	53,093	68,933
Interest Income Recognized	621	808	1,941	2,301
Real estate – commercial mortgage
Impaired loans
Unpaid Contractual Principal Balance	1,521		1,521		901
Recorded Investment With Allowance	1,337		1,337		728
Recorded Investment With No Allowance	152		152		165
Total Recorded Investment	1,489		1,489		893
Related Allowance	104		104		6
Average Recorded Investment	1,511	899	1,545	915
Interest Income Recognized	12	8	43	25
Real estate – commercial mortgage \| Receivables Acquired with Deteriorated Credit Quality
Impaired loans
Unpaid Contractual Principal Balance	171,754		171,754		186,720
Recorded Investment With Allowance	63,323		63,323		65,108
Recorded Investment With No Allowance	81,930		81,930		91,230
Total Recorded Investment	145,253		145,253		156,338
Related Allowance	1,961		1,961		892
Average Recorded Investment	141,780	174,394	144,530	177,039
Interest Income Recognized	1,705	2,578	5,610	6,886
Installment loans to individuals
Impaired loans
Unpaid Contractual Principal Balance	245		245		165
Recorded Investment With Allowance	244		244		154
Recorded Investment With No Allowance	0		0		9
Total Recorded Investment	244		244		163
Related Allowance	4		4		4
Average Recorded Investment	244	167	244	169
Interest Income Recognized	0	0	0	0
Installment loans to individuals \| Receivables Acquired with Deteriorated Credit Quality
Impaired loans
Unpaid Contractual Principal Balance	9,009		9,009		1,761
Recorded Investment With Allowance	701		701		698
Recorded Investment With No Allowance	4,277		4,277		940
Total Recorded Investment	4,978		4,978		1,638
Related Allowance	2		2		$ 1
Average Recorded Investment	1,608	1,812	1,616	1,865
Interest Income Recognized	$ 18	$ 18	$ 54	$ 55

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5258-111524

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Section 50
-Paragraph 14A
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