Loans (Non-Accrual Loans, Segregated by Class of Loans) (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	$ 83,467	$ 59,925
Commercial Portfolio Segment [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	25,111	34,108
Commercial and Industrial, Energy [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	21,180	636
Commercial Real Estate, Buildings, Land and Other [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	34,519	19,639
Construction Loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	569	2,792
Residential Portfolio Segment [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	1,862	2,212
Consumer Portfolio Segment [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	$ 226	$ 538