Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Impact of Modifications Classified as Troubled Debt Restructurings (Details) - Troubled Debt Restructurings [Member] $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($) Contract	Jun. 30, 2018 USD ($) Contract	Jun. 30, 2019 USD ($) Contract	Jun. 30, 2018 USD ($) Contract
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	8	21	18	26
Pre-Modification Outstanding Recorded Investment	$ 5,961	$ 10,935	$ 15,131	$ 13,524
Post-Modification Outstanding Recorded Investment	$ 5,847	$ 10,477	$ 15,017	$ 13,066
Construction, Land Development and Other Land [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract		1		1
Pre-Modification Outstanding Recorded Investment		$ 22		$ 22
Post-Modification Outstanding Recorded Investment		$ 22		$ 22
Secured by 1-4 Family Residential Properties [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	5	12	7	16
Pre-Modification Outstanding Recorded Investment	$ 793	$ 1,634	$ 879	$ 1,752
Post-Modification Outstanding Recorded Investment	$ 792	$ 1,193	$ 878	$ 1,311
Secured by Nonfarm, Nonresidential Properties [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	1		1
Pre-Modification Outstanding Recorded Investment	$ 5,055		$ 5,055
Post-Modification Outstanding Recorded Investment	$ 5,055		$ 5,055
Commercial and Industrial Loans [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	2	5	8	6
Pre-Modification Outstanding Recorded Investment	$ 113	$ 9,275	$ 9,167	$ 11,746
Post-Modification Outstanding Recorded Investment		$ 9,258	$ 9,054	$ 11,729
Consumer Loans [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract		3	2	3
Pre-Modification Outstanding Recorded Investment		$ 4	$ 30	$ 4
Post-Modification Outstanding Recorded Investment		$ 4	$ 30	$ 4