Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI (4) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 KeyRatios LoanPool CreditRiskGrade	Dec. 31, 2013
Financing Receivable Aging [Abstract]
Current	$ 5,842,659	$ 5,714,900
Past Due 30 - 89 Days	15,240	15,445
Nonaccrual	63,998	65,238
Total LHFI	5,923,766	5,798,881
Number of days used as baseline in evaluating collateral documentation exceptions for loan policy	90 days
Loan amount used as baseline in credit quality review for loan policy	100
Number of key quality ratios	6
Number of individual credit risk grades	10
Number of primary commercial loan groups	9
Loans Secured by Real Estate [Member] | Construction Land Development and Other Land Loans [Member]
Financing Receivable Aging [Abstract]
Current	578,715	582,639
Past Due 30 - 89 Days	2,530	923
Nonaccrual	11,259	13,327
Total LHFI	592,658	596,889
Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member]
Financing Receivable Aging [Abstract]
Current	1,499,796	1,451,528
Past Due 30 - 89 Days	7,969	9,437
Nonaccrual	24,585	21,603
Total LHFI	1,533,781	1,485,564
Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member]
Financing Receivable Aging [Abstract]
Current	1,439,828	1,391,286
Past Due 30 - 89 Days	1,418	2,044
Nonaccrual	20,701	21,809
Total LHFI	1,461,947	1,415,139
Loans Secured by Real Estate [Member] | Other Loans Secured by Real Estate [Member]
Financing Receivable Aging [Abstract]
Current	191,851	188,030
Past Due 30 - 89 Days	63	5
Nonaccrual	1,307	1,327
Total LHFI	193,221	189,362
Consumer Loans [Member]
Financing Receivable Aging [Abstract]
Current	158,353	162,843
Past Due 30 - 89 Days	1,382	2,012
Nonaccrual	134	151
Total LHFI	160,153	165,308
Other Loans [Member]
Financing Receivable Aging [Abstract]
Current	774,074	788,253
Past Due 30 - 89 Days	4	17
Nonaccrual	561	735
Total LHFI	774,639	789,005
Commercial Portfolio Segment [Member]
Financing Receivable [Abstract]
Financing receivable commercial	4,295,362	4,213,735
Commercial Portfolio Segment [Member] | Pass [Member]
Financing Receivable [Abstract]
Financing receivable commercial	4,072,644	3,982,761
Commercial Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable [Abstract]
Financing receivable commercial	36,277	36,313
Commercial Portfolio Segment [Member] | Substandard [Member]
Financing Receivable [Abstract]
Financing receivable commercial	183,225	190,743
Commercial Portfolio Segment [Member] | Doubtful [Member]
Financing Receivable [Abstract]
Financing receivable commercial	3,216	3,918
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Construction Land Development and Other Land Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial	534,573	545,691
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Construction Land Development and Other Land Loans [Member] | Pass [Member]
Financing Receivable [Abstract]
Financing receivable commercial	484,794	493,380
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Construction Land Development and Other Land Loans [Member] | Special Mention [Member]
Financing Receivable [Abstract]
Financing receivable commercial	5,165	4,383
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Construction Land Development and Other Land Loans [Member] | Substandard [Member]
Financing Receivable [Abstract]
Financing receivable commercial	44,352	47,610
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Construction Land Development and Other Land Loans [Member] | Doubtful [Member]
Financing Receivable [Abstract]
Financing receivable commercial	262	318
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member]
Financing Receivable [Abstract]
Financing receivable commercial	132,953	128,068
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member] | Pass [Member]
Financing Receivable [Abstract]
Financing receivable commercial	123,788	119,640
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member] | Special Mention [Member]
Financing Receivable [Abstract]
Financing receivable commercial	1,566	479
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member] | Substandard [Member]
Financing Receivable [Abstract]
Financing receivable commercial	7,414	7,839
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member] | Doubtful [Member]
Financing Receivable [Abstract]
Financing receivable commercial	185	110
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member]
Financing Receivable [Abstract]
Financing receivable commercial	1,460,573	1,413,692
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Pass [Member]
Financing Receivable [Abstract]
Financing receivable commercial	1,368,632	1,313,470
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Special Mention [Member]
Financing Receivable [Abstract]
Financing receivable commercial	9,660	12,620
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Substandard [Member]
Financing Receivable [Abstract]
Financing receivable commercial	81,973	87,203
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Doubtful [Member]
Financing Receivable [Abstract]
Financing receivable commercial	308	399
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Other Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial	190,049	185,942
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Other Loans Secured by Real Estate [Member] | Pass [Member]
Financing Receivable [Abstract]
Financing receivable commercial	183,131	178,951
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Other Loans Secured by Real Estate [Member] | Special Mention [Member]
Financing Receivable [Abstract]
Financing receivable commercial	0	0
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Other Loans Secured by Real Estate [Member] | Substandard [Member]
Financing Receivable [Abstract]
Financing receivable commercial	6,680	6,756
Commercial Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Other Loans Secured by Real Estate [Member] | Doubtful [Member]
Financing Receivable [Abstract]
Financing receivable commercial	238	235
Commercial Portfolio Segment [Member] | Commercial and Industrial Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial	1,207,363	1,157,596
Commercial Portfolio Segment [Member] | Commercial and Industrial Loans [Member] | Pass [Member]
Financing Receivable [Abstract]
Financing receivable commercial	1,150,067	1,099,429
Commercial Portfolio Segment [Member] | Commercial and Industrial Loans [Member] | Special Mention [Member]
Financing Receivable [Abstract]
Financing receivable commercial	19,826	18,771
Commercial Portfolio Segment [Member] | Commercial and Industrial Loans [Member] | Substandard [Member]
Financing Receivable [Abstract]
Financing receivable commercial	35,808	37,209
Commercial Portfolio Segment [Member] | Commercial and Industrial Loans [Member] | Doubtful [Member]
Financing Receivable [Abstract]
Financing receivable commercial	1,662	2,187
Commercial Portfolio Segment [Member] | Consumer Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial	253	496
Commercial Portfolio Segment [Member] | Consumer Loans [Member] | Pass [Member]
Financing Receivable [Abstract]
Financing receivable commercial	253	496
Commercial Portfolio Segment [Member] | Consumer Loans [Member] | Special Mention [Member]
Financing Receivable [Abstract]
Financing receivable commercial	0	0
Commercial Portfolio Segment [Member] | Consumer Loans [Member] | Substandard [Member]
Financing Receivable [Abstract]
Financing receivable commercial	0	0
Commercial Portfolio Segment [Member] | Consumer Loans [Member] | Doubtful [Member]
Financing Receivable [Abstract]
Financing receivable commercial	0	0
Commercial Portfolio Segment [Member] | Other Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial	769,598	782,250
Commercial Portfolio Segment [Member] | Other Loans [Member] | Pass [Member]
Financing Receivable [Abstract]
Financing receivable commercial	761,979	777,395
Commercial Portfolio Segment [Member] | Other Loans [Member] | Special Mention [Member]
Financing Receivable [Abstract]
Financing receivable commercial	60	60
Commercial Portfolio Segment [Member] | Other Loans [Member] | Substandard [Member]
Financing Receivable [Abstract]
Financing receivable commercial	6,998	4,126
Commercial Portfolio Segment [Member] | Other Loans [Member] | Doubtful [Member]
Financing Receivable [Abstract]
Financing receivable commercial	561	669
Consumer Portfolio Segment [Member]
Financing Receivable Aging [Abstract]
Current	1,596,026	1,552,447
Past Due 30 - 89 Days	9,014	11,095
Past Due 90 Days or More	1,715	3,298
Nonaccrual	21,649	18,306
Subtotal	1,628,404	1,585,146
Total LHFI	5,923,766	5,798,881
Consumer Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Construction Land Development and Other Land Loans [Member]
Financing Receivable Aging [Abstract]
Current	57,524	50,850
Past Due 30 - 89 Days	399	131
Past Due 90 Days or More	0	0
Nonaccrual	162	217
Subtotal	58,085	51,198
Total LHFI	592,658	596,889
Consumer Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member]
Financing Receivable Aging [Abstract]
Current	1,370,812	1,327,624
Past Due 30 - 89 Days	7,232	8,937
Past Due 90 Days or More	1,430	2,996
Nonaccrual	21,354	17,939
Subtotal	1,400,828	1,357,496
Total LHFI	1,533,781	1,485,564
Consumer Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member]
Financing Receivable Aging [Abstract]
Current	1,374	1,439
Past Due 30 - 89 Days	0	8
Past Due 90 Days or More	0	0
Nonaccrual	0	0
Subtotal	1,374	1,447
Total LHFI	1,461,947	1,415,139
Consumer Portfolio Segment [Member] | Loans Secured by Real Estate [Member] | Other Loans Secured by Real Estate [Member]
Financing Receivable Aging [Abstract]
Current	3,172	3,418
Past Due 30 - 89 Days	0	2
Past Due 90 Days or More	0	0
Nonaccrual	0	0
Subtotal	3,172	3,420
Total LHFI	193,221	189,362
Consumer Portfolio Segment [Member] | Commercial and Industrial Loans [Member]
Financing Receivable Aging [Abstract]
Current	3	13
Past Due 30 - 89 Days	0	5
Past Due 90 Days or More	1	0
Nonaccrual	0	0
Subtotal	4	18
Total LHFI	1,207,367	1,157,614
Consumer Portfolio Segment [Member] | Consumer Loans [Member]
Financing Receivable Aging [Abstract]
Current	158,100	162,348
Past Due 30 - 89 Days	1,383	2,012
Past Due 90 Days or More	284	302
Nonaccrual	133	150
Subtotal	159,900	164,812
Total LHFI	160,153	165,308
Consumer Portfolio Segment [Member] | Other Loans [Member]
Financing Receivable Aging [Abstract]
Current	5,041	6,755
Past Due 30 - 89 Days	0	0
Past Due 90 Days or More	0	0
Nonaccrual	0	0
Subtotal	5,041	6,755
Total LHFI	$ 774,639	$ 789,005