Summary of Significant Accounting Policies - Schedule of Potential Weighted Common Shares Outstanding that were Excluded from Computation of Diluted Net Loss per Share of Common Stock (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Employee share based awards [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential common shares excluded from computation of net loss per share	11,345,742	14,339,572	13,538,610	14,396,259
Convertible senior notes [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential common shares excluded from computation of net loss per share	2,345,823	2,517,573	2,150,258	2,301,823
Warrant issued in May 2013 [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential common shares excluded from computation of net loss per share	998,101	1,177,659	702,123	858,019