Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI (6) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014 Scale Factor Loan	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	$ 66,448	$ 78,738	$ 89,518
Loans charged-off	(13,226)	(13,478)	(31,376)
Recoveries	15,183	14,609	13,830
Net recoveries (charge-offs)	1,957	1,131	(17,546)
Provision for loan losses, LHFI	1,211	(13,421)	6,766
Balance at end of period	69,616	66,448	78,738
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Total	69,616	66,448	78,738
Number of Loan Types For Commercial Portfolio	9
Maximum value of commercial LHFI which were subject to further refinement of allowance for loan loss methodology	500
Number Of Unique Qualitative Factors Used To Analyze Consumer Loans	5
Number of Risk Rate Factors For Commercial Loans	450
The Minimum Score For Qualitative Risk Factor	0
The Maximum Score For Qualitative Risk Factor	100
Additional provision due to revision of methodology	2,222	1,600	1,400
Allowance for Loan Loses, LHFI [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	66,448	78,738
Loans charged-off	(13,226)	(13,478)
Recoveries	15,183	14,609
Provision for loan losses, LHFI	1,211	(13,421)
Balance at end of period	69,616	66,448
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	12,764	5,181
Collectively	56,852	61,267
Total	69,616	66,448
Real Estate Secured Financing Receivable [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
Loans charged-off	(1,100)	(1,441)
Recoveries	3,608	3,077
Provision for loan losses, LHFI	(2,600)	(10,309)
Balance at end of period	13,073	13,165
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	2,767	988
Collectively	10,306	12,177
Total	13,073	13,165
Real Estate Secured Financing Receivable [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
Loans charged-off	(2,505)	(1,298)
Recoveries	922	427
Provision for loan losses, LHFI	1,627	(2,453)
Balance at end of period	9,677	9,633
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	450	191
Collectively	9,227	9,442
Total	9,677	9,633
Real Estate Secured Financing Receivable [Member] \| 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
Loans charged-off	(390)	(1,002)
Recoveries	944	225
Provision for loan losses, LHFI	(1,703)	(647)
Balance at end of period	18,523	19,672
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	2,787	2,307
Collectively	15,736	17,365
Total	18,523	19,672
Real Estate Secured Financing Receivable [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
Loans charged-off	(277)	(910)
Recoveries	0	229
Provision for loan losses, LHFI	338	564
Balance at end of period	2,141	2,080
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	52	123
Collectively	2,089	1,957
Total	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	15,522	14,319
Loans charged-off	(2,092)	(1,371)
Recoveries	2,657	2,298
Provision for loan losses, LHFI	3,830	276
Balance at end of period	19,917	15,522
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	6,449	1,253
Collectively	13,468	14,269
Total	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	2,405	3,087
Loans charged-off	(1,965)	(2,425)
Recoveries	3,883	4,798
Provision for loan losses, LHFI	(2,174)	(3,055)
Balance at end of period	2,149	2,405
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	0	2
Collectively	2,149	2,403
Total	2,149	2,405
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
Loans charged-off	(4,897)	(5,031)
Recoveries	3,169	3,555
Provision for loan losses, LHFI	1,893	2,203
Balance at end of period	4,136	3,971
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	259	317
Collectively	3,877	3,654
Total	$ 4,136	$ 3,971

Maximum value of commercial LHFI which were subject to further refinement of allowance for loan loss methodology.

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- Definition

The number of unique loan types the commercial portfolio was delineated into for analysis of loan loss allowance.

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The number of risk rate factors utilized for the commercial portfolio.

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The number of unique qualitative factors used to evaluate the consumer loan portfolio for loan loss allowance.

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The provision for loan losses on loans held-for-sale.

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When presenting a range of scores, the highest potential score under the assessment procedure.

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When presenting a range of scores, the lowest potential score under the assessment procedure.

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- Definition

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953423-111524

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The effect of a change in method or methods for calculating the allowance for credit losses on the current period provision.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The increase (decrease) in the allowance for credit losses related to financing receivables.

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-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

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Amount of recovery of financing receivables doubtful of collection that were previously charged off.

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-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

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-Paragraph 11B

-Subparagraph (c)(4)

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Amount of direct write-downs of financing receivables charged against the allowance.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (c)(3)

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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7(d))

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-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Subparagraph d

-Article 9

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-Name Accounting Standards Codification

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 6

-Section L

-Subsection 1

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