Income Taxes - Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal	$ 0	$ 0	$ 0
State	699	1	(1)
Foreign	620	580	992
Total Current	1,319	581	991
Deferred:
Federal	0	0	0
State	0	0	0
Foreign	93	35	(115)
Total Deferred	93	35	(115)
Provision for income taxes	$ 1,412	$ 616	$ 876