Commitments and Contingencies - Narrative (Details) - USD ($) $ in Thousands		1 Months Ended	12 Months Ended
	Dec. 21, 2017	Oct. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	May 10, 2017	Mar. 31, 2016
Licenses, Royalties and Collaborative Agreements and Commitments
Purchase obligation, due in second year		$ 600	$ 608
Purchase obligation, renewal option, term		5 years
Purchase obligation, automatic renewal, term		5 years
Proceeds from issuance of warrants			207	$ 190	$ 0
Landlord contributions toward tenant improvements							$ 2,000
Tenant improvements			1,700
Rent expense			$ 5,600	$ 4,800	$ 4,900
ICT
Licenses, Royalties and Collaborative Agreements and Commitments
Proceeds from license fees received and issuance of warrants	$ 5,200
Proceeds from license fees received	$ 1,200
License agreement, contingent consideration, asset						$ 8,000