Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Nonaccrual LHFI by Loan Type (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Loan Portfolio [Abstract]
Total nonaccrual LHFI	$ 74,144	$ 49,234
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	2,746	3,323
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	19,079	20,329
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	20,661	8,482
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	185	402
Commercial and Industrial Loans [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	26,086	15,824
Consumer Loans [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	491	300
Other Loans [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	$ 4,896	$ 574