Summary of Significant Accounting Policies - Summarized Unaudited Financial Information for the Equity Method Investments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Operating expenses	$ 89,703	$ 75,723	$ 174,588	$ 159,694
Operating loss	(35,270)	(23,222)	(66,651)	(63,755)
Other	18,128	(22,347)	21,546	(43,772)
Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Current assets	67,361		67,361		$ 77,761
Non-current assets	13,109		13,109		11,040
Total assets	80,470		80,470		88,801
Current liabilities	12,950		12,950		11,588
Non-current liabilities	3,177		3,177		0
Total liabilities	16,127		16,127		11,588
Net assets	64,343		64,343		$ 77,213
Revenues	87	47	117	329
Operating expenses	10,092	14,383	23,435	32,043
Operating loss	(10,005)	(14,336)	(23,318)	(31,714)
Other	(68)	1,424	(63)	1,427
Net loss	$ (10,073)	$ (12,912)	$ (23,381)	$ (30,287)