Marketable Securities - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Investments Debt And Equity Securities [Abstract]
Marketable securities	$ 395,100,000	$ 0
Marketable securities unrealized loss, Less than twelve months	280,300,000
Marketable securities unrealized loss, more than twelve months	0
Unrealized loss, net	100,000
Marketable securities remaining maturities greater than two years	$ 0