Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI (6) (Details) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2015 USD ($) Loan Market Factor	Mar. 31, 2015 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) Scale	Jun. 30, 2014 USD ($)
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period		$ 69,616			$ 69,616
Provision for loan losses, LHFI	$ 1,033			$ 351	2,818	$ (454)
Balance at end of period	71,166				71,166
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Total	$ 71,166	$ 69,616			$ 71,166
Number of loan types for commercial portfolio | Loan	9
Number of unique qualitative factors used to analyze consumer loans | Market	5
Number of risk rate factors for commercial loans | Factor	450
Length of loss emergence period in the quantitative portion of the allowance for loan loss methodology for commercial LHFI		1 year 6 months
Additional provision amount quantitative portion of the allowance for loan loss methodology for commercial LHFI		$ 2,300
Minimum score for qualitative risk factor | Scale					0
Maximum score for qualitative risk factor | Scale					100
Amount of provision recapture resulting from the elimination of cap and floors for criticized risk ratings in the qualitative portion of the allowance for loan loss methodology for commercial LHFI		1,800
Amount of provision recapture resulting from market region distribution related to qualitative portion of the allowance for loan loss methodology for commercial LHFI		2,100
Amount of provision recapture resulting from market region distribution related to quantitative portion of the allowance for loan loss methodology for commercial LHFI		785
Additional provision due to revision of methodology		1,100	$ 822	1,400
Maximum value of commercial LHFI which were subject to further refinement of allowance for loan loss methodology			500
Allowance for Loan Loses, LHFI [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period		69,616	66,648		$ 69,616	66,448
Loans charged-off					(7,282)	(6,836)
Recoveries					6,014	7,490
Net (charge-offs) recoveries					(1,268)	654
Provision for loan losses, LHFI					2,818	(454)
Balance at end of period	$ 71,166			66,648	71,166	66,648
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	14,220			6,041
Collectively	56,946			60,607
Total	71,166	69,616	66,648	66,648	69,616	66,448
Construction, Land Development And Other Land Properties [Member] | 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		13,073	11,035		13,073	13,165
Loans charged-off					(928)	(76)
Recoveries					350	3,217
Provision for loan losses, LHFI					1,418	(5,271)
Balance at end of period	13,913			11,035	13,913	11,035
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	3,007			2,895
Collectively	10,906			8,140
Total	13,913	13,073	11,035	11,035	13,073	13,165
Secured by 1-4 Family Residential Properties [Member] | 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		9,677	10,454		9,677	9,633
Loans charged-off					(1,195)	(1,634)
Recoveries					106	255
Provision for loan losses, LHFI					229	2,200
Balance at end of period	8,817			10,454	8,817	10,454
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	469			308
Collectively	8,348			10,146
Total	8,817	9,677	10,454	10,454	9,677	9,633
Secured by Nonfarm, Nonresidential Properties [Member] | 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		18,523	18,584		18,523	19,672
Loans charged-off					(158)	(240)
Recoveries					392	94
Provision for loan losses, LHFI					(292)	(942)
Balance at end of period	18,465			18,584	18,465	18,584
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	3,295			1,642
Collectively	15,170			16,942
Total	18,465	18,523	18,584	18,584	18,523	19,672
Other Real Estate Secured [Member] | 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		2,141	2,463		2,141	2,080
Loans charged-off					(24)	(262)
Recoveries					3	0
Provision for loan losses, LHFI					(160)	645
Balance at end of period	1,960			2,463	1,960	2,463
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	46			53
Collectively	1,914			2,410
Total	1,960	2,141	2,463	2,463	2,141	2,080
Commercial and Industrial Loans [Member] | Allowance for Loan Loses, LHFI [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period		19,917	16,940		19,917	15,522
Loans charged-off					(1,256)	(1,656)
Recoveries					1,432	286
Provision for loan losses, LHFI					2,715	2,788
Balance at end of period	22,808			16,940	22,808	16,940
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	7,196			884
Collectively	15,612			16,056
Total	22,808	19,917	16,940	16,940	19,917	15,522
Consumer Loans [Member] | Allowance for Loan Loses, LHFI [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period		2,149	2,334		2,149	2,405
Loans charged-off					(1,012)	(883)
Recoveries					1,897	1,973
Provision for loan losses, LHFI					(1,150)	(1,161)
Balance at end of period	1,884			2,334	1,884	2,334
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	0			0
Collectively	1,884			2,334
Total	1,884	2,149	2,334	2,334	2,149	2,405
State and Other Political Subdivision Loans [Member] | Allowance for Loan Loses, LHFI [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period		1,314	1,906		1,314	1,205
Loans charged-off					0	0
Recoveries					0	0
Provision for loan losses, LHFI					(713)	701
Balance at end of period	601			1,906	601	1,906
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	0			0
Collectively	601			1,906
Total	601	1,314	1,906	1,906	1,314	1,205
Other Loans [Member] | Allowance for Loan Loses, LHFI [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period		2,822	2,932		2,822	2,766
Loans charged-off					(2,709)	(2,085)
Recoveries					1,834	1,665
Provision for loan losses, LHFI					771	586
Balance at end of period	2,718			2,932	2,718	2,932
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	207			259
Collectively	2,511			2,673
Total	$ 2,718	$ 2,822	$ 2,932	$ 2,932	$ 2,822	$ 2,766