Income Taxes - Components of Provision for Annual Income Taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current:
State	$ 1,000	$ 1,000	$ 1,000
Foreign	6,000	11,000	6,000
Total current	7,000	12,000	7,000
Deferred:
U.S. Federal		(4,000)
Total deferred		(4,000)
Provision for income taxes	$ 7,000	$ 8,000	$ 7,000