Deferred Tax Assets (Liabilities) Classified in Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Non-current deferred tax assets, net	$ 4,574	$ 2,791
Non-current deferred tax liabilities, net	(93,643)	(141,752)
Net deferred tax liabilities	$ (89,069)	$ (138,961)