Computation of Basic and Diluted Earnings per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net loss, basic	$ (23,848)	$ (77,211)	$ (117,042)
Less: gain on common stock held by the NQDC	0	(710)	0
Net loss, diluted	$ (23,848)	$ (77,921)	$ (117,042)
Weighted-average common shares outstanding, basic	179,039	177,061	174,427
Common stock held by the NQDC	0	207	0
Weighted-average common shares outstanding, diluted	179,039	177,268	174,427
Net loss per common share, basic (in usd per share)	$ (0.13)	$ (0.44)	$ (0.67)
Net loss per common share, diluted (in usd per share)	$ (0.13)	$ (0.44)	$ (0.67)