Income Taxes - Components of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current:
Federal	$ 0	$ 0	$ 0
State	7	21	0
Foreign	445	88	256
Total	452	109	256
Deferred:
Federal	0	0	0
State	0	0	0
Foreign	0	0	0
Total	0	0	0
Provision for income taxes	$ 452	$ 109	$ 256