Summary of Significant Accounting Policies - Summarized Financial Data (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Operating expenses	$ 61,283	$ 36,244	$ 244,576	$ 91,839
Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Current assets	12,225		12,225		$ 63,627
Non-current assets	462		462		1,259
Total assets	12,687		12,687		64,886
Current liabilities	10,121		10,121		15,346
Non-current liabilities	0		0		570
Total liabilities	10,121		10,121		15,916
Net assets	2,566		2,566		$ 48,970
Revenues	330	834	1,389	1,753
Operating expenses	7,020	17,052	114,023	46,266
Loss from operations	(6,690)	(16,218)	(112,634)	(44,513)
Other	(34)	5,854	(33)	11,543
Net loss	$ (6,724)	$ (10,364)	$ (112,667)	$ (32,970)