Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Loan Portfolio [Abstract]
Total LHFI	$ 6,333,651	$ 5,798,881
Less Allowance For Loan Losses, LHFI	70,134	66,448
Net LHFI	6,263,517	5,732,433
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	88,314	65,238
LHFI, Collectively Evaluated For Impairment	6,245,337	5,733,643
Total LHFI	6,333,651	5,798,881
Loans Secured by Real Estate [Member] | Construction Land Development and Other Land [Member]
Loan Portfolio [Abstract]
Total LHFI	580,794	596,889
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	20,286	13,327
LHFI, Collectively Evaluated For Impairment	560,508	583,562
Total LHFI	580,794	596,889
Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member]
Loan Portfolio [Abstract]
Total LHFI	1,625,480	1,485,564
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	27,017	21,603
LHFI, Collectively Evaluated For Impairment	1,598,463	1,463,961
Total LHFI	1,625,480	1,485,564
Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member]
Loan Portfolio [Abstract]
Total LHFI	1,560,901	1,415,139
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	23,885	21,809
LHFI, Collectively Evaluated For Impairment	1,537,016	1,393,330
Total LHFI	1,560,901	1,415,139
Loans Secured by Real Estate [Member] | Other Real Estate Properties [Member]
Loan Portfolio [Abstract]
Total LHFI	239,819	189,362
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	1,203	1,327
LHFI, Collectively Evaluated For Impairment	238,616	188,035
Total LHFI	239,819	189,362
Commercial and Industrial Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	1,246,753	1,157,614
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	15,178	6,286
LHFI, Collectively Evaluated For Impairment	1,231,575	1,151,328
Total LHFI	1,246,753	1,157,614
Consumer Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	168,813	165,308
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	160	151
LHFI, Collectively Evaluated For Impairment	168,653	165,157
Total LHFI	168,813	165,308
Other Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	911,091	789,005
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	585	735
LHFI, Collectively Evaluated For Impairment	910,506	788,270
Total LHFI	$ 911,091	$ 789,005