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		9 Months Ended
	Sep. 30, 2019 USD ($) Contract	Sep. 30, 2018 USD ($) Contract	Sep. 30, 2019 USD ($) Contract	Sep. 30, 2018 USD ($) Contract
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	4	12	22	38
Pre-Modification Outstanding Recorded Investment	$ 113	$ 11,274	$ 15,244	$ 24,798
Post-Modification Outstanding Recorded Investment	$ 102	$ 10,183	$ 15,119	$ 23,249
Secured by 1-4 Family Residential Properties [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	4	3	11	19
Pre-Modification Outstanding Recorded Investment	$ 113	$ 121	$ 992	$ 1,873
Post-Modification Outstanding Recorded Investment	$ 102	$ 121	$ 980	$ 1,432
Commercial and Industrial Loans [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract		9	8	15
Pre-Modification Outstanding Recorded Investment		$ 11,153	$ 9,167	$ 22,899
Post-Modification Outstanding Recorded Investment		$ 10,062	$ 9,054	$ 21,791
Construction, Land Development and Other Land [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract				1
Pre-Modification Outstanding Recorded Investment				$ 22
Post-Modification Outstanding Recorded Investment				$ 22
Secured by Nonfarm, Nonresidential Properties [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract			1
Pre-Modification Outstanding Recorded Investment			$ 5,055
Post-Modification Outstanding Recorded Investment			$ 5,055
Consumer Loans [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract			2	3
Pre-Modification Outstanding Recorded Investment			$ 30	$ 4
Post-Modification Outstanding Recorded Investment			$ 30	$ 4