Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Impaired Financing Receivables (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2019	Dec. 31, 2018
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	$ 55,089	$ 62,921
Total LHFI With No Related Allowance Recorded	29,583	25,553
Total LHFI With an Allowance Recorded	21,486	30,282
Total LHFI Recorded Investment	51,069	55,835
Related Allowance	4,334	6,354
Average Recorded Investment	53,452	46,920
Commercial and Industrial Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	31,463	37,786
Total LHFI With No Related Allowance Recorded	12,192	12,893
Total LHFI With an Allowance Recorded	17,197	17,824
Total LHFI Recorded Investment	29,389	30,717
Related Allowance	3,139	4,334
Average Recorded Investment	30,053	26,725
Consumer Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	30	2
Total LHFI With No Related Allowance Recorded	0	0
Total LHFI With an Allowance Recorded	30	2
Total LHFI Recorded Investment	30	2
Related Allowance	0	0
Average Recorded Investment	16	6
State and Other Political Subdivision Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	8,533	8,688
Total LHFI With No Related Allowance Recorded	8,303	4,079
Total LHFI With an Allowance Recorded	0	4,516
Total LHFI Recorded Investment	8,303	8,595
Related Allowance	0	516
Average Recorded Investment	8,449	4,297
Other Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	1,378	1,418
Total LHFI With No Related Allowance Recorded	230	230
Total LHFI With an Allowance Recorded	974	1,052
Total LHFI Recorded Investment	1,204	1,282
Related Allowance	974	1,052
Average Recorded Investment	1,244	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	945	1,794
Total LHFI With No Related Allowance Recorded	652	1,528
Total LHFI With an Allowance Recorded	20	24
Total LHFI Recorded Investment	672	1,552
Related Allowance	0	0
Average Recorded Investment	1,112	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	5,652	4,951
Total LHFI With No Related Allowance Recorded	1,688	95
Total LHFI With an Allowance Recorded	3,010	3,868
Total LHFI Recorded Investment	4,698	3,963
Related Allowance	30	39
Average Recorded Investment	4,330	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	7,088	8,282
Total LHFI With No Related Allowance Recorded	6,518	6,728
Total LHFI With an Allowance Recorded	255	2,748
Total LHFI Recorded Investment	6,773	9,476
Related Allowance	191	413
Average Recorded Investment	8,124	8,898
Loans Secured by Real Estate [Member] \| Other Real Estate Secured [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	0	0
Total LHFI With No Related Allowance Recorded	0	0
Total LHFI With an Allowance Recorded	0	248
Total LHFI Recorded Investment	0	248
Related Allowance	0	0
Average Recorded Investment	$ 124	$ 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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