Allowance for Probable Loan Losses (Non-accrual Basis By Loan Class) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Loan loss allowances, financing receivable past due
Non-accrual loans, total	$ 31,967	$ 37,245
Commercial
Loan loss allowances, financing receivable past due
Non-accrual loans, total	21,294	22,369
Commercial Real Estate: Other Construction and Land Development
Loan loss allowances, financing receivable past due
Non-accrual loans, total	3,587	4,776
Commercial Real Estate: Farmland & Commercial
Loan loss allowances, financing receivable past due
Non-accrual loans, total	5,532	8,314
Commercial Real Estate: Multifamily
Loan loss allowances, financing receivable past due
Non-accrual loans, total	532	552
Residential First Lien
Loan loss allowances, financing receivable past due
Non-accrual loans, total	424	655
Residential Junior Lien
Loan loss allowances, financing receivable past due
Non-accrual loans, total	166	166
Consumer
Loan loss allowances, financing receivable past due
Non-accrual loans, total	42	26
Foreign
Loan loss allowances, financing receivable past due
Non-accrual loans, total	$ 390	$ 387