Significant Accounting Policies - Reconciliation of Net Loss to Net Loss Attributable to Common Stockholders (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share [Abstract]
Net loss	$ (64,965)	$ (8,949)
Weighted average number of common shares used in net loss per share - basic and diluted	82,507,813	6,330,843
Net loss per share - basic and diluted	$ (0.79)	$ (1.41)