Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI (6) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2014 Loan Market Factor	Jun. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Scale Loan Market Factor	Sep. 30, 2013	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				$ 66,448
Provision for loan losses, LHFI	3,058		(3,624)	2,604	(11,438)
Balance at end of period	70,134			70,134		66,448
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Total	70,134			70,134		66,448
Number of loan types for commercial portfolio	9			9
Number of unique qualitative factors used to analyze consumer loans	5			5
Number of risk rate factors for commercial loans	450			450
Minimum score for qualitative risk factor				0
Maximum score for qualitative risk factor				100
Additional provision due to revision of methodology	822	1,400				1,600
Allowance for Loan Loses, LHFI [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				66,448	78,738	78,738
Loans charged-off				(10,052)	(10,173)
Recoveries				11,134	11,505
Net recoveries (charge-offs)				1,082	1,332
Provision for loan losses, LHFI				2,604	(11,438)
Balance at end of period	70,134		68,632	70,134	68,632
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	10,725		9,706	10,725	9,706
Collectively	59,409		58,926	59,409	58,926
Total	70,134		68,632	70,134	68,632
Loans Secured by Real Estate [Member] | Construction Land Development and Other Land [Member] | Allowance for Loan Loses, LHFI [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				13,165	21,838	21,838
Loans charged-off				(604)	(1,091)
Recoveries				3,413	2,561
Provision for loan losses, LHFI				(6,139)	(7,419)
Balance at end of period	9,835		15,889	9,835	15,889
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	2,607		957	2,607	957
Collectively	7,228		14,932	7,228	14,932
Total	9,835		15,889	9,835	15,889
Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member] | Allowance for Loan Loses, LHFI [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				9,633	12,957	12,957
Loans charged-off				(2,306)	(839)
Recoveries				861	363
Provision for loan losses, LHFI				1,986	(3,723)
Balance at end of period	10,174		8,758	10,174	8,758
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	431		260	431	260
Collectively	9,743		8,498	9,743	8,498
Total	10,174		8,758	10,174	8,758
Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Allowance for Loan Loses, LHFI [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				19,672	21,096	21,096
Loans charged-off				(240)	(572)
Recoveries				400	64
Provision for loan losses, LHFI				1,099	(1,828)
Balance at end of period	20,931		18,760	20,931	18,760
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	2,163		2,733	2,163	2,733
Collectively	18,768		16,027	18,768	16,027
Total	20,931		18,760	20,931	18,760
Loans Secured by Real Estate [Member] | Other Loans Secured by Real Estate [Member] | Allowance for Loan Loses, LHFI [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				2,080	2,197	2,197
Loans charged-off				(277)	(910)
Recoveries				0	80
Provision for loan losses, LHFI				571	497
Balance at end of period	2,374		1,864	2,374	1,864
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	57		37	57	37
Collectively	2,317		1,827	2,317	1,827
Total	2,374		1,864	2,374	1,864
Commercial and Industrial Loans [Member] | Allowance for Loan Loses, LHFI [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				15,522	14,319	14,319
Loans charged-off				(1,787)	(1,225)
Recoveries				1,321	2,190
Provision for loan losses, LHFI				4,490	2,004
Balance at end of period	19,546		17,288	19,546	17,288
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	5,203		5,393	5,203	5,393
Collectively	14,343		11,895	14,343	11,895
Total	19,546		17,288	19,546	17,288
Consumer Loans [Member] | Allowance for Loan Loses, LHFI [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				2,405	3,087	3,087
Loans charged-off				(1,304)	(1,789)
Recoveries				2,760	3,561
Provision for loan losses, LHFI				(1,631)	(2,256)
Balance at end of period	2,230		2,603	2,230	2,603
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	1		2	1	2
Collectively	2,229		2,601	2,229	2,601
Total	2,230		2,603	2,230	2,603
Other Loans [Member] | Allowance for Loan Loses, LHFI [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				3,971	3,244	3,244
Loans charged-off				(3,534)	(3,747)
Recoveries				2,379	2,686
Provision for loan losses, LHFI				2,228	1,287
Balance at end of period	5,044		3,470	5,044	3,470
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	263		324	263	324
Collectively	4,781		3,146	4,781	3,146
Total	$ 5,044		$ 3,470	$ 5,044	$ 3,470