Revenue Recognition (Additional Information) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained deficit		$ (511,127)		$ (511,127)			$ (500,044)
Revenue	[1]	15,724	$ 21,605	35,374	$ 41,296
Long-term accounts receivable		300		300
Deferred revenue		2,500		2,500
Decrease in deferred revenue				1,000
Revenue recognized				200
Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained deficit						$ 1,000
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue		$ 1,100		$ 2,400
Deferred revenue recorded to retained earnings						$ 800

[1] Quarters ended June 30,Components of Revenue2018 2017License Fees4,529 9,651Service Revenue11,195 11,954Net Revenue15,724 21,605 Six Months Ended June 30,Components of Revenue2018 2017License Fees$11,943 $16,804Service Revenue23,431 24,492Net Revenue$35,374 $41,296