Income Tax - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income tax expense	$ 0	$ 0	$ 0	$ 0
Federal and state effective tax rate before valuation allowance			24.00%
Unrecognized tax benefits	$ 2,500,000		$ 2,500,000		$ 2,200,000
Accrued interest and penalties related to uncertain tax positions			$ 0		$ 0