Loans (Non-Accrual Loans, Segregated by Class of Loans) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	$ 89,744	$ 94,338
Commercial and Industrial, Energy [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	1,150
Commercial and Industrial, Other Commercial [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	45,158	43,874
Commercial Real Estate, Buildings, Land and Other [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	38,631	43,820
Commercial Real Estate, Construction [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	1,100	1,329
Consumer Real Estate [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	2,773	4,587
Consumer and Other [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	$ 932	$ 728