Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Impaired Financing Receivables (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2019	Dec. 31, 2018
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	$ 46,196	$ 62,921
Total LHFI With No Related Allowance Recorded	25,238	25,553
Total LHFI With an Allowance Recorded	16,478	30,282
Total LHFI Recorded Investment	41,716	55,835
Related Allowance	4,377	6,354
Average Recorded Investment	48,775	46,920
Commercial and Industrial Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	26,786	37,786
Total LHFI With No Related Allowance Recorded	11,898	12,893
Total LHFI With an Allowance Recorded	12,543	17,824
Total LHFI Recorded Investment	24,441	30,717
Related Allowance	3,435	4,334
Average Recorded Investment	27,579	26,725
Consumer Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	24	2
Total LHFI With No Related Allowance Recorded	0	0
Total LHFI With an Allowance Recorded	23	2
Total LHFI Recorded Investment	23	2
Related Allowance	0	0
Average Recorded Investment	12	6
State and Other Political Subdivision Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	4,079	8,688
Total LHFI With No Related Allowance Recorded	4,079	4,079
Total LHFI With an Allowance Recorded	0	4,516
Total LHFI Recorded Investment	4,079	8,595
Related Allowance	0	516
Average Recorded Investment	6,337	4,297
Other Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	1,330	1,418
Total LHFI With No Related Allowance Recorded	230	230
Total LHFI With an Allowance Recorded	685	1,052
Total LHFI Recorded Investment	915	1,282
Related Allowance	685	1,052
Average Recorded Investment	1,099	804
Loans Secured by Real Estate [Member] \| Construction, Land Development and Other Land [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	937	1,794
Total LHFI With No Related Allowance Recorded	631	1,528
Total LHFI With an Allowance Recorded	18	24
Total LHFI Recorded Investment	649	1,552
Related Allowance	0	0
Average Recorded Investment	1,100	1,738
Loans Secured by Real Estate [Member] \| Secured by 1-4 Family Residential Properties [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	6,079	4,951
Total LHFI With No Related Allowance Recorded	2,244	95
Total LHFI With an Allowance Recorded	2,880	3,868
Total LHFI Recorded Investment	5,124	3,963
Related Allowance	29	39
Average Recorded Investment	4,543	4,328
Loans Secured by Real Estate [Member] \| Secured by Nonfarm, Nonresidential Properties [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	6,892	8,282
Total LHFI With No Related Allowance Recorded	6,087	6,728
Total LHFI With an Allowance Recorded	329	2,748
Total LHFI Recorded Investment	6,416	9,476
Related Allowance	228	413
Average Recorded Investment	7,946	8,898
Loans Secured by Real Estate [Member] \| Other Real Estate Secured [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	69	0
Total LHFI With No Related Allowance Recorded	69	0
Total LHFI With an Allowance Recorded	0	248
Total LHFI Recorded Investment	69	248
Related Allowance	0	0
Average Recorded Investment	$ 159	$ 124

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=118936363&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=118936363&loc=d3e5258-111524

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953550-111524

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