Allowance for Probable Loan Losses (Details 3) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Loan loss allowances, financing receivable past due
Non-accrual loans, total	$ 74,587	$ 71,768
Commercial
Loan loss allowances, financing receivable past due
Non-accrual loans, total	34,384	31,929
Commercial real estate: other construction and land development
Loan loss allowances, financing receivable past due
Non-accrual loans, total	24,240	26,410
Commercial real estate: farmland and commercial
Loan loss allowances, financing receivable past due
Non-accrual loans, total	14,335	11,681
Commercial real estate: multifamily
Loan loss allowances, financing receivable past due
Non-accrual loans, total	324	353
Residential: first lien
Loan loss allowances, financing receivable past due
Non-accrual loans, total	1,178	1,175
Residential: junior lien
Loan loss allowances, financing receivable past due
Non-accrual loans, total	64	175
Consumer
Loan loss allowances, financing receivable past due
Non-accrual loans, total	49	45
Foreign
Loan loss allowances, financing receivable past due
Non-accrual loans, total	$ 13