Summary of Significant Accounting Policies - Summarized Financial Data of Equity Method Investments (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Operating expenses	$ 141,892	$ 81,783	$ 88,931
Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Current assets	19,540	26,655
Non-current assets	109	27
Total assets	19,649	26,682
Current liabilities	4,520	1,276
Net assets	15,129	25,406
Revenues, net	940	1,032	0
Operating expenses	17,289	18,498	578
Loss from operations	(16,349)	(17,466)	(578)
Other	35	137	(1)
Net loss	$ (16,314)	$ (17,329)	$ (579)