Net Income (Loss) Per Share Attributable to Common Shareholders - Schedule of Antidilutive Securities not Include in Computation of Net Income (Loss) per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities not include in computation of net income (loss) per share	2,769,844	6,877,463	2,441,297	6,877,463
Outstanding Options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities not include in computation of net income (loss) per share	2,612,354	6,698,579	2,326,824	6,698,579
Unvested Restricted Common Shares [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities not include in computation of net income (loss) per share	157,490	178,884	114,473	178,884