Description of Business, Basis of Presentation and Consolidation and Significant Accounting Policies - Recent Accounting Pronouncements - Revenue (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Current assets:
Unbilled receivable	$ 12,702	$ 16,307
Equity:
Accumulated deficit	$ (594,929)	(333,446)	$ (330,517)
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Current assets:
Unbilled receivable		16,307
Equity:
Accumulated deficit		$ 16,307