Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Loan Portfolio [Abstract]
Total LHFI	$ 5,923,766	$ 5,798,881
Less Allowance For Loan Losses, LHFI	67,518	66,448
Net LHFI	5,856,248	5,732,433
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	63,998	65,238
LHFI, Collectively Evaluated For Impairment	5,859,768	5,733,643
Total LHFI	5,923,766	5,798,881
Loans Secured by Real Estate [Member] | Construction Land Development and Other Land Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	592,658	596,889
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	11,259	13,327
LHFI, Collectively Evaluated For Impairment	581,399	583,562
Total LHFI	592,658	596,889
Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member]
Loan Portfolio [Abstract]
Total LHFI	1,533,781	1,485,564
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	24,585	21,603
LHFI, Collectively Evaluated For Impairment	1,509,196	1,463,961
Total LHFI	1,533,781	1,485,564
Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member]
Loan Portfolio [Abstract]
Total LHFI	1,461,947	1,415,139
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	20,701	21,809
LHFI, Collectively Evaluated For Impairment	1,441,246	1,393,330
Total LHFI	1,461,947	1,415,139
Loans Secured by Real Estate [Member] | Other Real Estate Properties [Member]
Loan Portfolio [Abstract]
Total LHFI	193,221	189,362
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	1,307	1,327
LHFI, Collectively Evaluated For Impairment	191,914	188,035
Total LHFI	193,221	189,362
Commercial and Industrial Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	1,207,367	1,157,614
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	5,451	6,286
LHFI, Collectively Evaluated For Impairment	1,201,916	1,151,328
Total LHFI	1,207,367	1,157,614
Consumer Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	160,153	165,308
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	134	151
LHFI, Collectively Evaluated For Impairment	160,019	165,157
Total LHFI	160,153	165,308
Other Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	774,639	789,005
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	561	735
LHFI, Collectively Evaluated For Impairment	774,078	788,270
Total LHFI	$ 774,639	$ 789,005