Allowance for Probable Loan Losses (Details 3) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Loan loss allowances, financing receivable past due
Non-accrual loans, total	$ 86,452	$ 71,768
Commercial
Loan loss allowances, financing receivable past due
Non-accrual loans, total	34,450	31,929
Commercial real estate: other construction and land development
Loan loss allowances, financing receivable past due
Non-accrual loans, total	34,053	26,410
Commercial real estate: farmland and commercial
Loan loss allowances, financing receivable past due
Non-accrual loans, total	14,775	11,681
Commercial real estate: multifamily
Loan loss allowances, financing receivable past due
Non-accrual loans, total	314	353
Residential: first lien
Loan loss allowances, financing receivable past due
Non-accrual loans, total	1,234	1,175
Residential: junior lien
Loan loss allowances, financing receivable past due
Non-accrual loans, total	1,576	175
Consumer
Loan loss allowances, financing receivable past due
Non-accrual loans, total	37	45
Foreign
Loan loss allowances, financing receivable past due
Non-accrual loans, total	$ 13