Significant Components of Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ (375)	$ (495)	$ 1,509
State	(99)	(496)	120
Foreign	581	445	966
Total current	107	(546)	2,595
Deferred	(2,134)	(50,535)	(56,800)
Income taxes	$ (2,027)	$ (51,081)	$ (54,205)