Allowance for Probable Loan Losses (Details 4) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2011	Dec. 31, 2010
Loan loss allowances, impaired financing receivable
Period of charge off for past due unsecured commercial loans (in days)	90
Commercial | Loans with Related Allowance
Loan loss allowances, impaired financing receivable
Recorded Investment	$ 22,942	$ 23,062
Unpaid Principal Balance	22,942	23,071
Related Allowance	7,937	8,138
Average Recorded Investment	22,948	23,096
Interest Recognized	20	42
Commercial | Loans with No Related Allowance
Loan loss allowances, impaired financing receivable
Recorded Investment	423	364
Unpaid Principal Balance	916	980
Average Recorded Investment	458	993
Interest Recognized	9	30
Commercial real estate: other construction and land development | Loans with Related Allowance
Loan loss allowances, impaired financing receivable
Recorded Investment	8,136	10,603
Unpaid Principal Balance	8,147	10,645
Related Allowance	371	592
Average Recorded Investment	8,177	10,622
Commercial real estate: other construction and land development | Loans with No Related Allowance
Loan loss allowances, impaired financing receivable
Recorded Investment	24,538	66,604
Unpaid Principal Balance	24,595	66,755
Average Recorded Investment	20,433	68,608
Interest Recognized	2	2
Commercial real estate: farmland and commercial | Loans with Related Allowance
Loan loss allowances, impaired financing receivable
Recorded Investment	22,468	17,841
Unpaid Principal Balance	22,489	17,878
Related Allowance	4,334	3,441
Average Recorded Investment	21,199	18,475
Interest Recognized	413	860
Commercial real estate: farmland and commercial | Loans with No Related Allowance
Loan loss allowances, impaired financing receivable
Recorded Investment	8,872	4,003
Unpaid Principal Balance	10,336	5,606
Average Recorded Investment	1,366	5,594
Commercial real estate: multifamily | Loans with No Related Allowance
Loan loss allowances, impaired financing receivable
Recorded Investment	440	473
Unpaid Principal Balance	440	473
Average Recorded Investment	454	500
Residential: first lien | Loans with No Related Allowance
Loan loss allowances, impaired financing receivable
Recorded Investment	1,799	2,015
Unpaid Principal Balance	1,937	2,143
Average Recorded Investment	1,816	2,297
Interest Recognized	3
Residential: junior lien | Loans with No Related Allowance
Loan loss allowances, impaired financing receivable
Recorded Investment	1,519	199
Unpaid Principal Balance	1,520	226
Average Recorded Investment	1,521	228
Interest Recognized	48
Consumer | Loans with No Related Allowance
Loan loss allowances, impaired financing receivable
Recorded Investment	1,100	29
Unpaid Principal Balance	1,105	46
Average Recorded Investment	1,281	49
Foreign | Loans with No Related Allowance
Loan loss allowances, impaired financing receivable
Recorded Investment	1	7
Unpaid Principal Balance	1	7
Average Recorded Investment	3	19
Loans with Related Allowance
Loan loss allowances, impaired financing receivable
Recorded Investment	53,546	51,506
Unpaid Principal Balance	53,578	51,594
Related Allowance	12,642	12,171
Average Recorded Investment	52,324	52,193
Interest Recognized	433	902
Loans with No Related Allowance
Loan loss allowances, impaired financing receivable
Recorded Investment	38,692	73,694
Unpaid Principal Balance	40,850	76,236
Average Recorded Investment	27,332	78,288
Interest Recognized	$ 62	$ 32