Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Loan Portfolio [Abstract]
Total LHFI	$ 5,577,382	$ 5,592,754
Less Allowance For Loan Losses, LHFI	72,825	78,738
Net LHFI	5,504,557	5,514,016
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	74,318	82,363
LHFI, Collectively Evaluated For Impairment	5,503,064	5,510,391
Total LHFI	5,577,382	5,592,754
Loans Secured by Real Estate [Member] | Construction Land Development and Other Land Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	519,263	468,975
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	16,259	27,105
LHFI, Collectively Evaluated For Impairment	503,004	441,870
Total LHFI	519,263	468,975
Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member]
Loan Portfolio [Abstract]
Total LHFI	1,414,871	1,497,480
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	23,837	27,114
LHFI, Collectively Evaluated For Impairment	1,391,034	1,470,366
Total LHFI	1,414,871	1,497,480
Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member]
Loan Portfolio [Abstract]
Total LHFI	1,406,930	1,410,264
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	18,418	18,289
LHFI, Collectively Evaluated For Impairment	1,388,512	1,391,975
Total LHFI	1,406,930	1,410,264
Loans Secured by Real Estate [Member] | Other Real Estate Properties [Member]
Loan Portfolio [Abstract]
Total LHFI	192,568	189,949
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	511	3,956
LHFI, Collectively Evaluated For Impairment	192,057	185,993
Total LHFI	192,568	189,949
Commercial and Industrial Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	1,169,327	1,169,513
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	14,193	4,741
LHFI, Collectively Evaluated For Impairment	1,155,134	1,164,772
Total LHFI	1,169,327	1,169,513
Consumer Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	160,318	171,660
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	267	360
LHFI, Collectively Evaluated For Impairment	160,051	171,300
Total LHFI	160,318	171,660
Other Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	714,105	684,913
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	833	798
LHFI, Collectively Evaluated For Impairment	713,272	684,115
Total LHFI	$ 714,105	$ 684,913