Marketable Securities - Summary of Fair Values and Unrealized Losses of Marketable Securities Held by the Company in an Unrealized Loss Position for Less Than 12 months and 12 Months or Greater (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	$ 282,894	$ 55,507
Less than 12 Months, Unrealized Losses	(755)	(55)
Total, Fair Value	282,894	55,507
Total, Unrealized Losses	(755)	(55)
Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	275,305	55,507
Less than 12 Months, Unrealized Losses	(754)	(55)
Total, Fair Value	275,305	55,507
Total, Unrealized Losses	(754)	$ (55)
U.S. Government and Federal Agency Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	7,589
Less than 12 Months, Unrealized Losses	(1)
Total, Fair Value	7,589
Total, Unrealized Losses	$ (1)