Fair value measurements - Summary of Fair Value of the Financial Instruments that are Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Level 1 [Member]
Assets:
Cash equivalents	$ 186,816	$ 220,383
Fair value, assets	205,844	243,527
Level 2 [Member]
Assets:
Cash equivalents	0	0
Fair value, assets	0
Level 3 [Member]
Assets:
Cash equivalents	0	0
Fair value, assets	0	0
U.S. Treasury bonds [Member] \| Level 1 [Member]
Assets:
Fair value, assets	15,110	23,144
U.S. Treasury bonds [Member] \| Level 2 [Member]
Assets:
Fair value, assets	0	0
Fair value, assets		0
U.S. Treasury bonds [Member] \| Level 3 [Member]
Assets:
Fair value, assets	0	$ 0
Certificates of deposit [Member] \| Level 1 [Member]
Assets:
Fair value, assets	3,918
Certificates of deposit [Member] \| Level 2 [Member]
Assets:
Fair value, assets	0
Certificates of deposit [Member] \| Level 3 [Member]
Assets:
Fair value, assets	$ 0

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

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- Definition

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.

+ References

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- References

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- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

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