Income Taxes - Components of Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal			$ 0
State	$ 220	$ 170	181
Foreign	1,477	1,238	1,442
Total current	1,697	1,408	1,623
Deferred:
Federal			0
State			0
Foreign	(929)		0
Total deferred	(929)		0
Total provision for income taxes	$ 768	$ 1,408	$ 1,623