Fair Value Measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	$ 63,973	$ 66,286
Recurring
Liabilities that are measured at fair value on a recurring basis
Assets, fair value	70,119	69,984
Recurring \| Level 1
Liabilities that are measured at fair value on a recurring basis
Assets, fair value	6,146	3,698
Recurring \| Level 2
Liabilities that are measured at fair value on a recurring basis
Assets, fair value	63,973	66,286
Recurring \| Level 3
Liabilities that are measured at fair value on a recurring basis
Assets, fair value	0	0
Commercial paper \| Recurring
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	13,242	8,994
Commercial paper \| Recurring \| Level 1
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
Commercial paper \| Recurring \| Level 2
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	13,242	8,994
Commercial paper \| Recurring \| Level 3
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
Corporate notes \| Recurring
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	48,156	35,911
Corporate notes \| Recurring \| Level 1
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
Corporate notes \| Recurring \| Level 2
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	48,156	35,911
Corporate notes \| Recurring \| Level 3
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
U.S. government securities
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	1,500	12,842
U.S. government securities \| Recurring
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	1,500	12,842
U.S. government securities \| Recurring \| Level 1
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
U.S. government securities \| Recurring \| Level 2
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	1,500	12,842
U.S. government securities \| Recurring \| Level 3
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
U.S. government agency bonds
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	1,075	5,001
U.S. government agency bonds \| Recurring
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	1,075	5,001
U.S. government agency bonds \| Recurring \| Level 1
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
U.S. government agency bonds \| Recurring \| Level 2
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	1,075	5,001
U.S. government agency bonds \| Recurring \| Level 3
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
U.S. asset-backed securities
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value		3,538
U.S. asset-backed securities \| Recurring
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	3,538
U.S. asset-backed securities \| Recurring \| Level 1
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
U.S. asset-backed securities \| Recurring \| Level 2
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	3,538
U.S. asset-backed securities \| Recurring \| Level 3
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
Money market funds \| Recurring
Liabilities that are measured at fair value on a recurring basis
Money market funds	6,146	3,698
Money market funds \| Recurring \| Level 1
Liabilities that are measured at fair value on a recurring basis
Money market funds	6,146	3,698
Money market funds \| Recurring \| Level 2
Liabilities that are measured at fair value on a recurring basis
Money market funds	0	0
Money market funds \| Recurring \| Level 3
Liabilities that are measured at fair value on a recurring basis
Money market funds	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of 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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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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