Marketable Securities - Summary of Company Marketable Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	$ 365,504	$ 183,623
Unrealized Gains	247	555
Unrealized Losses	(755)	(55)
Fair Value	364,996	184,123
U.S. Government and Federal Agency Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	7,590	12,782
Unrealized Gains		22
Unrealized Losses	(1)
Fair Value	7,589	12,804
Certificates of Deposit [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	1,466	1,956
Unrealized Gains	23	34
Fair Value	1,489	1,990
Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	353,423	165,850
Unrealized Gains	221	497
Unrealized Losses	(754)	(55)
Fair Value	352,890	166,292
Municipal Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	3,025	3,035
Unrealized Gains	3	2
Fair Value	$ 3,028	$ 3,037

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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