Fair Value Measurements - Summary of Financial Assets Recognized at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Marketable securities:
Investment in Kyverna Therapeutics, Inc.	$ 2,265	$ 4,390
Fair Value on Recurring Basis [Member]
Assets
Cash equivalents and restricted cash equivalents	76,058	66,898
Marketable securities:
Total marketable securities	580,220	672,548
Investment in Kyverna Therapeutics, Inc.	2,265	4,390
Total Assets	658,543	743,836
Fair Value on Recurring Basis [Member] \| U.S. Treasury and Other Government - Backed Securities [Member]
Marketable securities:
Total marketable securities	293,711	352,616
Fair Value on Recurring Basis [Member] \| Financial Institution Debt Securities [Member]
Marketable securities:
Total marketable securities	186,243	217,827
Fair Value on Recurring Basis [Member] \| Corporate Debt Securities [Member]
Marketable securities:
Total marketable securities	100,266	94,927
Fair Value on Recurring Basis [Member] \| Other Asset Backed Securities [Member]
Marketable securities:
Total marketable securities		7,178
Fair Value on Recurring Basis [Member] \| Level 1 [Member]
Assets
Cash equivalents and restricted cash equivalents	76,058	66,898
Marketable securities:
Total marketable securities	153,244	169,735
Investment in Kyverna Therapeutics, Inc.	2,265	4,390
Total Assets	231,567	241,023
Fair Value on Recurring Basis [Member] \| Level 1 [Member] \| U.S. Treasury and Other Government - Backed Securities [Member]
Marketable securities:
Total marketable securities	153,244	169,735
Fair Value on Recurring Basis [Member] \| Level 2 [Member]
Marketable securities:
Total marketable securities	426,976	502,813
Total Assets	426,976	502,813
Fair Value on Recurring Basis [Member] \| Level 2 [Member] \| U.S. Treasury and Other Government - Backed Securities [Member]
Marketable securities:
Total marketable securities	140,467	182,881
Fair Value on Recurring Basis [Member] \| Level 2 [Member] \| Financial Institution Debt Securities [Member]
Marketable securities:
Total marketable securities	186,243	217,827
Fair Value on Recurring Basis [Member] \| Level 2 [Member] \| Corporate Debt Securities [Member]
Marketable securities:
Total marketable securities	$ 100,266	94,927
Fair Value on Recurring Basis [Member] \| Level 2 [Member] \| Other Asset Backed Securities [Member]
Marketable securities:
Total marketable securities		$ 7,178

Fair value portion of asset recognized for present right to economic benefit.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Fair value portion of investments in an entity not consolidated. Includes, but is not limited to, investments in an entity that is affiliated with the reporting entity by means of direct or indirect ownership, an entity in which the reporting entity shares control of the entity with another party or group, an entity which the company has significant influence, but does not have control and subsidiaries that are not required to be consolidated and are accounted for using the equity or cost method.

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