Basis of Presentation and Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit	$ (163,907)	$ (89,615)
Deferred revenue	97,872	163,073
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit	$ (32,854)	(46,900)
Deferred revenue		$ 46,900