Summary of Significant Accounting Policies - Summarized Financial Data (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Operating expenses	$ 62,321	$ 29,869	$ 183,293	$ 55,595
Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Current assets	15,259		15,259		$ 63,627
Non-current assets	209		209		1,259
Total assets	15,468		15,468		64,886
Current liabilities	9,181		9,181		15,346
Non-current liabilities	0		0		570
Total liabilities	9,181		9,181		15,916
Net assets	6,287		6,287		$ 48,970
Revenues	423	504	1,059	919
Operating expenses	22,845	16,294	106,914	29,214
Loss from operations	(22,422)	(15,790)	(105,855)	(28,295)
Other	2	5,608	1	5,689
Net loss	$ (22,420)	$ (10,182)	$ (105,854)	$ (22,606)