Summary of Significant Accounting Policies - Anti-Dilutive Securities Excluded from the Computation of Diluted Net Loss per Share (Detail) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted loss per share	8,227	8,076	8,227	8,076
Common Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted loss per share	8,126	7,949	8,126	7,949
Incentive Awards [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted loss per share	101	127	101	127