Revenue Recognition - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Revenue from External Customer [Line Items]
Deferred commissions	$ 200		$ 200
Revenue recognized, previously deferred	2,200	$ 1,100
Revenue recognized, would have previously been deferred until later in 2018	100
Deferred revenue	$ 12,865		$ 13,095
Minimum [Member]
Revenue from External Customer [Line Items]
Average duration of the data creation process	12 months
Payment terms of non-exclusive license contracts	30 days
Maximum [Member]
Revenue from External Customer [Line Items]
Average duration of the data creation process	18 months
Payment terms of non-exclusive license contracts	12 months