Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI (1) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013 Region	Mar. 31, 2012	Dec. 31, 2012
Loan and Lease Receivables, Impaired [Abstract]
Unpaid Principal Balance	$ 113,275,000		$ 119,818,000
Total LHFI With No Related Allowance Recorded	23,625,000		23,190,000
Total LHFI With an Allowance Recorded	59,697,000		59,173,000
Total Carrying Amount	83,322,000		82,363,000
Related Allowance	11,013,000		10,504,000
Average Recorded Investment	82,843,000		96,410,000
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	83,300,000		82,400,000
Minimum loan amount for loan to be individually assessed for impairment	500,000
Nonaccrual financing receivable, specifically evaluated for impairment	33,000,000		40,600,000
Nonaccrual financing receivable, allowance for credit losses, specifically evaluated for impairment	3,500,000		5,900,000
Nonaccrual financing receivable, allowance for credit losses, charge-offs, specifically evaluated for impairment	986,000	1,400,000
Nonaccrual financing receivable specifically evaluated for impairment allowance for credit losses provisions	1,300,000	864,000
Nonaccrual financing receivable, not specifically evaluated for impairment	50,300,000		41,800,000
Nonaccrual financing receivable, allowance for credit losses, not specifically evaluated for impairment	7,600,000		4,600,000
Classified as Troubled Debt Restructuring LHFI	24,700,000		24,300,000
TDRs comprised of credits with interest only payments	16,800,000		21,600,000
Financing receivable, related allowance	4,000,000		4,300,000
Financing receivable, related charge-offs	60,000	563,000
Loans Secured by Real Estate [Member] | Construction Land Development And Other Financing Receivable [Member]
Loan and Lease Receivables, Impaired [Abstract]
Unpaid Principal Balance	39,955,000		46,558,000
Total LHFI With No Related Allowance Recorded	10,483,000		9,571,000
Total LHFI With an Allowance Recorded	13,960,000		17,534,000
Total Carrying Amount	24,443,000		27,105,000
Related Allowance	3,514,000		4,992,000
Average Recorded Investment	25,774,000		33,759,000
Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member]
Loan and Lease Receivables, Impaired [Abstract]
Unpaid Principal Balance	35,509,000		35,155,000
Total LHFI With No Related Allowance Recorded	2,461,000		2,533,000
Total LHFI With an Allowance Recorded	24,688,000		24,581,000
Total Carrying Amount	27,149,000		27,114,000
Related Allowance	1,117,000		1,469,000
Average Recorded Investment	27,131,000		25,731,000
Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member]
Loan and Lease Receivables, Impaired [Abstract]
Unpaid Principal Balance	20,528,000		23,337,000
Total LHFI With No Related Allowance Recorded	7,976,000		8,184,000
Total LHFI With an Allowance Recorded	9,904,000		10,105,000
Total Carrying Amount	17,880,000		18,289,000
Related Allowance	2,170,000		2,296,000
Average Recorded Investment	18,085,000		21,135,000
Loans Secured by Real Estate [Member] | Other Real Estate Secured Financing Receivable [Member]
Loan and Lease Receivables, Impaired [Abstract]
Unpaid Principal Balance	1,543,000		6,036,000
Total LHFI With No Related Allowance Recorded	555,000		566,000
Total LHFI With an Allowance Recorded	485,000		3,390,000
Total Carrying Amount	1,040,000		3,956,000
Related Allowance	32,000		760,000
Average Recorded Investment	2,498,000		4,914,000
Commercial and Industrial Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Unpaid Principal Balance	11,629,000		7,251,000
Total LHFI With No Related Allowance Recorded	2,100,000		2,336,000
Total LHFI With an Allowance Recorded	6,953,000		2,405,000
Total Carrying Amount	9,053,000		4,741,000
Related Allowance	3,584,000		640,000
Average Recorded Investment	6,897,000		9,444,000
Consumer Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Unpaid Principal Balance	525,000		624,000
Total LHFI With No Related Allowance Recorded	0		0
Total LHFI With an Allowance Recorded	277,000		360,000
Total Carrying Amount	277,000		360,000
Related Allowance	2,000		5,000
Average Recorded Investment	319,000		592,000
Other Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Unpaid Principal Balance	3,586,000		857,000
Total LHFI With No Related Allowance Recorded	50,000		0
Total LHFI With an Allowance Recorded	3,430,000		798,000
Total Carrying Amount	3,480,000		798,000
Related Allowance	594,000		342,000
Average Recorded Investment	$ 2,139,000		$ 835,000