Marketable Securities - Additional Information (Detail) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Marketable Securities [Line Items]
Realized gains or losses on marketable securities	$ 0	$ 0
Investments that matured beyond five years	$ 0	$ 0
Minimum [Member]
Marketable Securities [Line Items]
Available-for-sales Securities, non-current, maturity period	1 year
Maximum [Member]
Marketable Securities [Line Items]
Available-for-sales Securities, non-current, maturity period	5 years