Income Taxes - Components of the Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ 0	$ 0
State	1	2
Foreign	24	24
Total current tax expense	25	26
Deferred:
Federal	0	0
State	0	0
Foreign	0	0
Total deferred tax benefit	0	0
Total tax expense	$ 25	$ 26