Summary of Significant Accounting Policies - Adoption of Topic 606 and ASC 842, Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss	$ (91,420)	$ (75,155)
Net cash used in operating activities	(45,754)	(37,480)
Net cash used in investing activities	(164,711)	(162,364)
Net cash provided by financing activities	212,003	197,419
Net change in cash and restricted cash	1,538	(2,425)
Cash and restricted cash, beginning of period	241,790	224,363
Cash and restricted cash, end of period	$ 243,328	221,938
Previously Reported
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss		(73,084)
Net cash used in operating activities		(29,107)
Net cash used in investing activities		(170,759)
Net cash provided by financing activities		197,293
Net change in cash and restricted cash		(2,573)
Cash and restricted cash, beginning of period		206,364
Cash and restricted cash, end of period		203,791
Adoption Impact | Accounting Standards Update 2014-09, Topic 230 and ASC 842
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss		(2,071)
Net cash used in operating activities		(8,373)
Net cash used in investing activities		8,395
Net cash provided by financing activities		126
Net change in cash and restricted cash		148
Cash and restricted cash, beginning of period		17,999
Cash and restricted cash, end of period		$ 18,147