Marketable Securities - Summary of Company Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	$ 305,538	$ 183,623
Unrealized Gains	51	555
Unrealized Losses	(476)	(55)
Fair Value	305,113	184,123
U.S. Government and Federal Agency Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	25,003	12,782
Unrealized Gains		22
Unrealized Losses	(23)
Fair Value	24,980	12,804
Certificates of Deposit [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	2,939	1,956
Unrealized Gains	10	34
Unrealized Losses	(1)
Fair Value	2,948	1,990
Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	274,592	165,850
Unrealized Gains	41	497
Unrealized Losses	(452)	(55)
Fair Value	274,181	166,292
Municipal Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	3,004	3,035
Unrealized Gains		2
Fair Value	$ 3,004	$ 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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