Loans - Net (Charge-Offs)/Recoveries, Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
(Net charge-offs)/Recoveries	$ (1,974)	$ (1,794)	$ (3,970)	$ (5,676)
Commercial and industrial, Energy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
(Net charge-offs)/Recoveries	1	460	3	447
Commercial and industrial, Other commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
(Net charge-offs)/Recoveries	(1,683)	(1,594)	(2,535)	(3,277)
Commercial real estate, Buildings, land and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
(Net charge-offs)/Recoveries	279	(400)	(28)	(2,018)
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
(Net charge-offs)/Recoveries	15	275	16	315
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
(Net charge-offs)/Recoveries	81	(27)	53	(4)
Consumer and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
(Net charge-offs)/Recoveries	$ (667)	$ (508)	$ (1,479)	$ (1,139)