Revenue by Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue, Major Customer [Line Items]
Revenue	$ 44,003	$ 45,986	$ 48,556	$ 42,612	$ 47,463	$ 52,122	$ 50,974	$ 42,366	$ 181,157	$ 192,925	$ 153,612
Sales | Geographic Concentration Risk
Revenue, Major Customer [Line Items]
Concentration risk									100.00%	100.00%	100.00%
United States
Revenue, Major Customer [Line Items]
Revenue									$ 123,209	$ 136,111	$ 107,228
United States | Sales | Geographic Concentration Risk
Revenue, Major Customer [Line Items]
Concentration risk									68.00%	70.60%	69.80%
Total International
Revenue, Major Customer [Line Items]
Revenue									$ 57,948	$ 56,814	$ 46,384
Total International | Sales | Geographic Concentration Risk
Revenue, Major Customer [Line Items]
Concentration risk									32.00%	29.40%	30.20%