Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI (1) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015 Region	Mar. 31, 2014	Dec. 31, 2014
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	$ 93,802,000		$ 96,365,000
Total LHFI With No Related Allowance Recorded	15,616,000		23,135,000
Total LHFI With an Allowance Recorded	61,392,000		56,208,000
Total LHFI Carrying Amount	77,008,000		79,343,000
Related Allowance	14,016,000		12,764,000
Average Recorded Investment	78,175,000		72,291,000
Maximum concentration of loan as a percentage of total LHFI (in hundredths)	10.00%
Key market regions	5
Carrying amounts of nonaccrual LHFI considered for impairment analysis	77,000,000		79,300,000
Minimum loan amount for loan to be individually assessed for impairment	500,000
Nonaccrual financing receivable, specifically evaluated for impairment	48,300,000		47,100,000
Nonaccrual financing receivable, allowance for credit losses, specifically evaluated for impairment	12,300,000		11,300,000
Nonaccrual financing receivable, allowance for credit losses, charge-offs, specifically evaluated for impairment	234,000	46,000
Nonaccrual financing receivable specifically evaluated for impairment allowance for credit losses provisions	825,000	536,000
Nonaccrual financing receivable, not specifically evaluated for impairment	28,700,000		32,200,000
Nonaccrual financing receivable, allowance for credit losses, not specifically evaluated for impairment	1,700,000		1,500,000
Amount held by company of foreclosure or in substance repossession of consumer mortgage LHFI classified as TDRs	451,000
TDRs Classified as Consumer mortgage LHFI in the process of formal disclosure	123,000
Classified as Troubled Debt Restructuring LHFI	10,800,000	13,400,000
TDRs comprised of credits with interest only payments	6,900,000	9,100,000
Financing receivable, related allowance	1,800,000	1,600,000
Financing receivable, related charge-offs	0	0
Loans Secured by Real Estate [Member] | Construction Land Development and Other Land [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	27,082,000		20,849,000
Total LHFI With No Related Allowance Recorded	5,360,000		7,411,000
Total LHFI With an Allowance Recorded	14,774,000		6,456,000
Total LHFI Carrying Amount	20,134,000		13,867,000
Related Allowance	4,097,000		2,767,000
Average Recorded Investment	17,001,000		13,597,000
Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	29,273,000		31,151,000
Total LHFI With No Related Allowance Recorded	1,465,000		1,650,000
Total LHFI With an Allowance Recorded	22,155,000		23,971,000
Total LHFI Carrying Amount	23,620,000		25,621,000
Related Allowance	429,000		450,000
Average Recorded Investment	24,621,000		23,612,000
Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	19,489,000		27,969,000
Total LHFI With No Related Allowance Recorded	6,293,000		12,868,000
Total LHFI With an Allowance Recorded	11,594,000		12,849,000
Total LHFI Carrying Amount	17,887,000		25,717,000
Related Allowance	2,728,000		2,787,000
Average Recorded Investment	21,801,000		23,763,000
Loans Secured by Real Estate [Member] | Other Real Estate Secured [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	812,000		1,594,000
Total LHFI With No Related Allowance Recorded	0		0
Total LHFI With an Allowance Recorded	723,000		1,318,000
Total LHFI Carrying Amount	723,000		1,318,000
Related Allowance	51,000		52,000
Average Recorded Investment	1,021,000		1,322,000
Commercial and Industrial Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	16,390,000		13,916,000
Total LHFI With No Related Allowance Recorded	2,498,000		1,206,000
Total LHFI With an Allowance Recorded	11,559,000		10,898,000
Total LHFI Carrying Amount	14,057,000		12,104,000
Related Allowance	6,502,000		6,449,000
Average Recorded Investment	13,080,000		9,195,000
Consumer Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	148,000		152,000
Total LHFI With No Related Allowance Recorded	0		0
Total LHFI With an Allowance Recorded	96,000		88,000
Total LHFI Carrying Amount	96,000		88,000
Related Allowance	0		0
Average Recorded Investment	92,000		120,000
State and Other Political Subdivision Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	0		0
Total LHFI With No Related Allowance Recorded	0		0
Total LHFI With an Allowance Recorded	0		0
Total LHFI Carrying Amount	0		0
Related Allowance	0		0
Average Recorded Investment	0		0
Other Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	608,000		734,000
Total LHFI With No Related Allowance Recorded	0		0
Total LHFI With an Allowance Recorded	491,000		628,000
Total LHFI Carrying Amount	491,000		628,000
Related Allowance	209,000		259,000
Average Recorded Investment	$ 559,000		$ 682,000