Income Taxes - Components of Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal		$ 0	$ 0	$ 0
State		2	7	21
Foreign		559	445	88
Total		561	452	109
Deferred:
Federal		0	0	0
State		0	0	0
Foreign		0	0	0
Total		0	0	0
Provision for income taxes	$ 0	$ 561	$ 452	$ 109