Net Income (Loss) Per Share of Common Stock - Shares excluded from Computation of Diluted Net Income (Loss) per Share (Detail) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share amount	90,254	92,247
Stock options and employee stock purchase plan [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share amount	35,905	22,985
Restricted Shares [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share amount	1,417	5,504
Restricted Stock Units (ZSUs) [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share amount	52,932	63,758