Commitments and Contingencies - Narrative (Details) - USD ($) $ in Thousands		1 Months Ended	12 Months Ended
	Dec. 21, 2017	Oct. 31, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Licenses, Royalties and Collaborative Agreements and Commitments
Purchase obligation, due in second year		$ 600	$ 711
Purchase obligation, renewal option, term		5 years
Purchase obligation, automatic renewal, term		5 years
Proceeds from issuance of warrants			0	$ 207	$ 190
Landlord contributions toward tenant improvements						$ 2,000
Tenant improvements			1,900
Rent expense			$ 5,500	$ 5,600	$ 4,800
ICT
Licenses, Royalties and Collaborative Agreements and Commitments
License Agreement, Initial Payment	$ 5,200