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, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Total	$ 72,445	$ 71,265
Allowance for Loan Losses, LHFI [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	3,882	3,260
Collectively	68,563	68,005
Total	72,445	71,265	$ 69,668	$ 67,619
Allowance for Loan Losses, LHFI [Member] | Commercial and Industrial Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	1,562	1,976
Collectively	20,089	20,035
Total	21,651	22,011	17,649	15,815
Allowance for Loan Losses, LHFI [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively	3,192	3,241
Total	3,192	3,241	2,804	2,879
Allowance for Loan Losses, LHFI [Member] | State and Other Political Subdivision Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually		0
Collectively	848	859
Total	848	859	816	809
Allowance for Loan Losses, LHFI [Member] | Other Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively	2,394	2,492
Total	2,394	2,492	2,004	1,821
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]
Individually	111	103
Collectively	8,415	8,982
Total	8,526	9,085	10,142	11,587
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	1,357	960
Collectively	9,430	9,387
Total	10,787	10,347	10,473	10,678
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	852	221
Collectively	21,056	20,746
Total	21,908	20,967	23,707	21,563
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	3,139	2,263
Total	$ 3,139	$ 2,263	$ 2,073	$ 2,467