Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Summary of Balance in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	$ 5,000	$ 6,400
Total	79,005	79,290
Allowance for Loan Losses, LHFI [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	5,040	6,354
Collectively	73,965	72,936
Total	79,005	79,290	$ 81,235	$ 76,733
Allowance for Loan Losses, LHFI [Member] \| Commercial and Industrial Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	3,407	4,334
Collectively	25,795	23,025
Total	29,202	27,359	29,017	22,851
Allowance for Loan Losses, LHFI [Member] \| Consumer Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively	3,148	2,890
Total	3,148	2,890	3,227	3,470
Allowance for Loan Losses, LHFI [Member] \| State and Other Political Subdivision Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	370	516
Collectively	422	474
Total	792	990	792	789
Allowance for Loan Losses, LHFI [Member] \| Other Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	1,006	1,052
Collectively	4,396	5,142
Total	5,402	6,194	3,953	4,666
Allowance for Loan Losses, LHFI [Member] \| Loans Secured by Real Estate [Member] \| Construction, Land Development and Other Land [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively	7,524	7,390
Total	7,524	7,390	7,826	7,865
Allowance for Loan Losses, LHFI [Member] \| Loans Secured by Real Estate [Member] \| Secured by 1-4 Family Residential Properties [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	32	39
Collectively	8,349	8,602
Total	8,381	8,641	9,591	10,874
Allowance for Loan Losses, LHFI [Member] \| Loans Secured by Real Estate [Member] \| Secured by Nonfarm, Nonresidential Properties [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	225	413
Collectively	21,254	21,963
Total	21,479	22,376	24,520	23,428
Allowance for Loan Losses, LHFI [Member] \| Loans Secured by Real Estate [Member] \| Other Real Estate Secured [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively	3,077	3,450
Total	$ 3,077	$ 3,450	$ 2,309	$ 2,790

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

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-Publisher FASB
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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

+ References

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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