Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI (3) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Financing Receivable, Modifications [Line Items]
Nonaccrual	$ 83,322	$ 82,363
Troubled Debt Restructurings [Member]
Financing Receivable, Modifications [Line Items]
Accruing	1,394	1,513
Nonaccrual	23,315	22,760
Total	24,709	24,273
Troubled Debt Restructurings [Member] | Construction Land Development and Other Land Loans [Member]
Financing Receivable, Modifications [Line Items]
Accruing	231	233
Nonaccrual	10,720	12,073
Total	10,951	12,306
Troubled Debt Restructurings [Member] | Secured by 1-4 Family Residential Properties [Member]
Financing Receivable, Modifications [Line Items]
Accruing	1,163	1,280
Nonaccrual	5,528	5,908
Total	6,691	7,188
Troubled Debt Restructurings [Member] | Secured by Nonfarm, Nonresidential Properties [Member]
Financing Receivable, Modifications [Line Items]
Accruing	0	0
Nonaccrual	3,454	4,582
Total	3,454	4,582
Troubled Debt Restructurings [Member] | Other Loans Secured by Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Accruing	0	0
Nonaccrual	2,677	197
Total	2,677	197
Troubled Debt Restructurings [Member] | Commercial And Industrial Loans [Member]
Financing Receivable, Modifications [Line Items]
Accruing	0
Nonaccrual	936
Total	$ 936