Restructuring - Additional Information (Detail) - USD ($)	6 Months Ended	9 Months Ended
	Jun. 30, 2019	Sep. 30, 2019	Sep. 30, 2020	Dec. 31, 2019
Research and Development Expense [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges		$ 1,900,000
General and Administrative Expense [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges		$ 600,000
Restructuring Plan, July 2018 [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges incurred			$ 7,400
Revised estimates during the year/ period	$ 2,000
Amounts accrued			0	$ 0
Restructuring Plan, November 6, 2018 [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges incurred				$ 1,600
Amounts accrued			$ 0