Loans (Net (Charge-Offs)/Recoveries, Segregated by Class of Loans) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	$ (15,528)	$ (9,210)	$ (32,597)
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	(6,535)	(2,911)	(28,431)
Commercial and Industrial, Energy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	(5,997)	(1,237)	(913)
Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	314	(2,348)	(381)
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	18	348	256
Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	(91)	(733)	(719)
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	$ (3,237)	$ (2,329)	$ (2,409)