Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Nonaccrual LHFI by Loan Type (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Loan Portfolio [Abstract]
Total nonaccrual LHFI	$ 61,307	$ 49,234
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	2,856	3,323
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	20,537	20,329
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	11,492	8,482
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	191	402
Commercial and Industrial Loans [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	25,410	15,824
Consumer Loans [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	325	300
Other Loans [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	$ 496	$ 574