Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financial assets
Available-for-sale marketable securities	$ 170,424	$ 219,807
Recurring [Member]
Financial assets
Total financial assets	193,823	251,898
U.S. Government Agency Obligations [Member]
Financial assets
Available-for-sale marketable securities	17,044	22,128
U.S. Government Agency Obligations [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	17,044	22,128
Corporate Bonds [Member]
Financial assets
Available-for-sale marketable securities	46,914	49,118
Corporate Bonds [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	46,914	49,118
Municipal Bonds [Member]
Financial assets
Available-for-sale marketable securities	17,942	11,684
Municipal Bonds [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	17,942	11,684
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Recurring [Member]
Financial assets
Total financial assets	23,399	32,091
Significant Other Observable Inputs (Level 2) [Member] \| Recurring [Member]
Financial assets
Total financial assets	170,424	219,807
Significant Other Observable Inputs (Level 2) [Member] \| U.S. Government Agency Obligations [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	17,044	22,128
Significant Other Observable Inputs (Level 2) [Member] \| Corporate Bonds [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	46,914	49,118
Significant Other Observable Inputs (Level 2) [Member] \| Municipal Bonds [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	17,942	11,684
Money Market Funds [Member] \| Recurring [Member]
Financial assets
Cash and cash equivalents	22,991	31,683
Restricted cash	408	408
Money Market Funds [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Recurring [Member]
Financial assets
Cash and cash equivalents	22,991	31,683
Restricted cash	408	408
U.S. Treasury Securities [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	10,070	20,750
U.S. Treasury Securities [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	10,070	20,750
Commercial Paper [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	78,454	116,127
Commercial Paper [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	$ 78,454	$ 116,127

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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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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Amount of cash and cash equivalents restricted as to withdrawal or usage, classified as noncurrent. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, 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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