Loss from Continuing Operations Before Provision for Income Tax (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
US	$ (84,207)	$ (113,679)	$ 129,361
Foreign	(2,528)	(3,603)	(3,697)
(Loss) income before income tax expense	$ (86,735)	$ (117,282)	$ 125,664