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, 2018 USD ($) Contract	Jun. 30, 2017 USD ($) Contract	Jun. 30, 2018 USD ($) Contract	Jun. 30, 2017 USD ($) Contract
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	21	10	26	18
Pre-Modification Outstanding Recorded Investment	$ 10,935	$ 1,078	$ 13,524	$ 1,753
Post-Modification Outstanding Recorded Investment	$ 10,477	$ 1,083	$ 13,066	$ 1,746
Secured by 1-4 Family Residential Properties [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	12	9	16	16
Pre-Modification Outstanding Recorded Investment	$ 1,634	$ 834	$ 1,752	$ 1,168
Post-Modification Outstanding Recorded Investment	$ 1,193	$ 839	$ 1,311	$ 1,177
Construction, Land Development and Other Land [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	1		1	1
Pre-Modification Outstanding Recorded Investment	$ 22		$ 22	$ 341
Post-Modification Outstanding Recorded Investment	$ 22		$ 22	$ 325
Commercial and Industrial Loans [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	5	1	6	1
Pre-Modification Outstanding Recorded Investment	$ 9,275	$ 244	$ 11,746	$ 244
Post-Modification Outstanding Recorded Investment	$ 9,258	$ 244	$ 11,729	$ 244
Consumer Loans [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	3		3
Pre-Modification Outstanding Recorded Investment	$ 4		$ 4
Post-Modification Outstanding Recorded Investment	$ 4		$ 4