Revenue - Cumulative Effect of Changes to Balance Sheet (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Other accrued liabilities		$ 4,893
Accumulated deficit	$ (103,222)	(102,298)	$ (102,503)
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Other accrued liabilities			5,098
Accumulated deficit			$ (102,503)
Adjustments Upon Adoption of ASC 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Other accrued liabilities		(205)
Accumulated deficit		$ 205