Summary of Significant Accounting Policies - Adoption of Topic 606 and ASC 842, Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss	$ (71,727)	$ (73,610)	$ (163,147)	$ (148,765)
Net cash used in operating activities			(111,181)	(49,171)
Net cash used in investing activities			(349,724)	(344,443)
Net cash provided by financing activities			489,518	402,196
Net change in cash and restricted cash(1)			28,613	8,582
Cash and restricted cash, beginning of period			241,790	224,363
Cash and restricted cash, end of period	$ 270,403	232,945	$ 270,403	232,945
Previously Reported
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss		(65,242)		(138,326)
Net cash used in operating activities				(33,457)
Net cash used in investing activities				(361,190)
Net cash provided by financing activities				399,604
Net change in cash and restricted cash(1)				4,957
Cash and restricted cash, beginning of period				206,364
Cash and restricted cash, end of period		211,321		211,321
Adoption Impact | Accounting Standards Update 2014-09, Topic 230 and ASC 842
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss				(10,439)
Net cash used in operating activities				(15,714)
Net cash used in investing activities				16,747
Net cash provided by financing activities				2,592
Net change in cash and restricted cash(1)				3,625
Cash and restricted cash, beginning of period				17,999
Cash and restricted cash, end of period		$ 21,624		$ 21,624