Net Loss per Share - Schedule of Potentially Dilutive Common Stock Equivalents (Detail) - shares shares in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Options to Purchase Common Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	2,398	2,818
RSUs [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	2,173	2,364
ESPP [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	3	5