Restructuring - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2020	Dec. 31, 2019
Research and Development Expense [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	$ 2,000,000	$ 1,900,000
General and Administrative Expense [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	$ 200,000	400,000
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