Loans - Non-Accrual Loans, Segregated by Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	$ 79,081	$ 89,744
Commercial and industrial, Energy [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	766	1,150
Commercial and industrial, Other commercial [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	34,695	45,158
Commercial real estate, Buildings, land and other [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	40,541	38,631
Commercial real estate, Construction [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	0	1,100
Consumer Real Estate [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	2,298	2,773
Consumer and Other [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	$ 781	$ 932