Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current
U.S. federal	$ 0	$ 0	$ 0
U.S. state	0	0	0
Non-U.S.	240	51	0
Total current	240	51	0
Deferred
U.S. federal	(9,164)	244,801	(43,814)
U.S. state	(1,903)	15,398	(4,311)
Non-U.S.	0	0	0
Total deferred	(11,067)	260,199	(48,125)
Valuation allowance	11,067	(260,199)	48,125
Total	$ 240	$ 51	$ 0