Summary of Continuous Unrealized Loss on Marketable Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule Of Held To Maturity Securities [Line Items]
Estimated Fair Value, Less Than 12 Months	$ 67,145	$ 67,009
Unrealized Loss, Less Than 12 Months	(36)	(37)
Estimated Fair Value, 12 Months or Greater	0	0
Unrealized Loss, 12 Months or Greater	0	0
Estimated Fair Value, Total	67,145	67,009
Unrealized Loss, Total	(36)	(37)
Commercial Paper
Schedule Of Held To Maturity Securities [Line Items]
Estimated Fair Value, Less Than 12 Months	63,026	62,440
Unrealized Loss, Less Than 12 Months	(35)	(36)
Estimated Fair Value, 12 Months or Greater	0	0
Unrealized Loss, 12 Months or Greater	0	0
Estimated Fair Value, Total	63,026	62,440
Unrealized Loss, Total	(35)	(36)
Corporate Bonds
Schedule Of Held To Maturity Securities [Line Items]
Estimated Fair Value, Less Than 12 Months	4,119	4,569
Unrealized Loss, Less Than 12 Months	(1)	(1)
Estimated Fair Value, 12 Months or Greater	0	0
Unrealized Loss, 12 Months or Greater	0	0
Estimated Fair Value, Total	4,119	4,569
Unrealized Loss, Total	$ (1)	$ (1)

Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss position for 12 months or longer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27337-111563

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in unrealized loss position.

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Fair value of investment in debt security measured at amortized cost (held-to-maturity), in unrealized loss position.

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss position for less than 12 months.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Section 50
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-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27337-111563

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Fair value of investment in debt security measured at amortized cost (held-to-maturity), in continuous unrealized loss position for less than 12 months.

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