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		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 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	5,666,686	14,917,083	16,527,336	15,426,144
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		2,710,738	1,959,492	2,454,778
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		1,463,838	629,782	1,084,627