Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Loan Portfolio [Abstract]
Total LHFI	$ 6,187,000	$ 5,798,881
Less Allowance For Loan Losses, LHFI	66,648	66,448
Net LHFI	6,120,352	5,732,433
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	71,118	65,238
LHFI, Collectively Evaluated For Impairment	6,115,882	5,733,643
Total LHFI	6,187,000	5,798,881
Loans Secured by Real Estate [Member] | Construction Land Development and Other Land Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	531,651	596,889
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	21,142	13,327
LHFI, Collectively Evaluated For Impairment	510,509	583,562
Total LHFI	531,651	596,889
Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member]
Loan Portfolio [Abstract]
Total LHFI	1,581,859	1,485,564
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	23,403	21,603
LHFI, Collectively Evaluated For Impairment	1,558,456	1,463,961
Total LHFI	1,581,859	1,485,564
Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member]
Loan Portfolio [Abstract]
Total LHFI	1,544,516	1,415,139
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	18,659	21,809
LHFI, Collectively Evaluated For Impairment	1,525,857	1,393,330
Total LHFI	1,544,516	1,415,139
Loans Secured by Real Estate [Member] | Other Real Estate Properties [Member]
Loan Portfolio [Abstract]
Total LHFI	250,383	189,362
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	1,233	1,327
LHFI, Collectively Evaluated For Impairment	249,150	188,035
Total LHFI	250,383	189,362
Commercial and Industrial Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	1,250,146	1,157,614
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	5,762	6,286
LHFI, Collectively Evaluated For Impairment	1,244,384	1,151,328
Total LHFI	1,250,146	1,157,614
Consumer Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	165,372	165,308
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	107	151
LHFI, Collectively Evaluated For Impairment	165,265	165,157
Total LHFI	165,372	165,308
Other Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	863,073	789,005
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	812	735
LHFI, Collectively Evaluated For Impairment	862,261	788,270
Total LHFI	$ 863,073	$ 789,005