Investments - Summary of Gross Unrealized Gains and Losses and Credit Losses (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 468,626	$ 683,006
Gross Unrealized Gains	956	437
Gross Unrealized Losses	(55)	(1,251)
Fair Value	469,527	682,192
U.S. Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	41,933	167,165
Gross Unrealized Gains	39	107
Gross Unrealized Losses	(8)	(347)
Fair Value	41,964	166,925
U.S. Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	230,869	210,491
Gross Unrealized Gains	715	191
Gross Unrealized Losses	(29)	(484)
Fair Value	231,555	210,198
International Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	88,715	97,698
Gross Unrealized Gains	180	99
Gross Unrealized Losses	(11)	(122)
Fair Value	88,884	97,675
U.S. Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	54,362	23,360
Gross Unrealized Gains	1	11
Gross Unrealized Losses	0	(1)
Fair Value	54,363	23,370
International Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	31,571	46,935
Gross Unrealized Gains	0	3
Gross Unrealized Losses	(1)	(38)
Fair Value	31,570	46,900
U.S. Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,203	8,830
Fair Value	2,203	8,830
U.S. Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	18,973	128,527
Gross Unrealized Gains	21	26
Gross Unrealized Losses	(6)	(259)
Fair Value	$ 18,988	$ 128,294