Revenue Recognition - Adoption of ASC Topic 606 (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jan. 02, 2018	Dec. 31, 2017
Net income (loss)
Net income (loss)	$ (28,920)	$ (3,515)
Stockholders' equity
Retained (deficit) / earnings	(163,603)			$ (136,274)
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Net income (loss)
Net income (loss)	$ 0
Stockholders' equity
Retained (deficit) / earnings			$ 0