Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Loan Portfolio [Abstract]
Total LHFI	$ 5,696,641	$ 5,592,754
Less Allowance For Loan Losses, LHFI	68,632	78,738
Net LHFI	5,628,009	5,514,016
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	73,381	82,363
LHFI, Collectively Evaluated For Impairment	5,623,260	5,510,391
Total LHFI	5,696,641	5,592,754
Loans Secured by Real Estate [Member] | Construction Land Development and Other Land Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	572,057	468,975
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	14,454	27,105
LHFI, Collectively Evaluated For Impairment	557,603	441,870
Total LHFI	572,057	468,975
Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member]
Loan Portfolio [Abstract]
Total LHFI	1,482,963	1,497,480
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	23,715	27,114
LHFI, Collectively Evaluated For Impairment	1,459,248	1,470,366
Total LHFI	1,482,963	1,497,480
Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member]
Loan Portfolio [Abstract]
Total LHFI	1,408,342	1,410,264
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	21,290	18,289
LHFI, Collectively Evaluated For Impairment	1,387,052	1,391,975
Total LHFI	1,408,342	1,410,264
Loans Secured by Real Estate [Member] | Other Real Estate Properties [Member]
Loan Portfolio [Abstract]
Total LHFI	196,328	189,949
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	503	3,956
LHFI, Collectively Evaluated For Impairment	195,825	185,993
Total LHFI	196,328	189,949
Commercial and Industrial Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	1,132,863	1,169,513
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	12,196	4,741
LHFI, Collectively Evaluated For Impairment	1,120,667	1,164,772
Total LHFI	1,132,863	1,169,513
Consumer Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	164,612	171,660
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	203	360
LHFI, Collectively Evaluated For Impairment	164,409	171,300
Total LHFI	164,612	171,660
Other Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	739,476	684,913
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	1,020	798
LHFI, Collectively Evaluated For Impairment	738,456	684,115
Total LHFI	$ 739,476	$ 684,913