Number of employees issued stock during period.

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Percentage of internal rate of return on investment .

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Restricted stock units description.

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Share based compensation arrangement by share based payment award award vest in maximum number of annual installments.

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Share based compensation arrangement by share based payment award rate of shares issuence.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of noncash expense for share-based payment arrangement.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Number of shares authorized for issuance under share-based payment arrangement.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Gross number of share options (or share units) granted during the period.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of share options (or share units) exercised during the current period.

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Equity Incentive Plan - Additional Information (Detail)	3 Months Ended		9 Months Ended		12 Months Ended
Equity Incentive Plan - Additional Information (Detail)	Sep. 30, 2021 USD ($) Installment shares	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) Installment $ / shares shares	Sep. 30, 2020 USD ($) $ / shares	Dec. 31, 2020 USD ($) employees $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option exercised					0	0
Stock-based compensation \| $			$ 2,998,000	$ 2,552,000	$ 3,435,000	$ 2,265,000
Number of employees issued stock during period \| employees					2
Restricted stock units, Description					market value equal to the greater of (1) $3.5 million for two employees, or $4 million for the other referenced employee or (2) an amount determined using a formula-based model (as defined in the respective employment agreements), as of the date of such grants.
Non Employee Director [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation \| $					$ 400,000	$ 700,000
Options granted					136,956	7,223
Performance Based Vesting Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period					10 years
Weighted average fair value granted \| $ / shares						$ 37.16
Performance Based Vesting Stock Option [Member] \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Internal rate of return on investment					70.00%
Restricted Stock Units [Member] \| Non Employee Director [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation \| $	$ 200,000	$ 200,000	$ 500,000	$ 200,000
Options granted			90,324
Restricted Stock Units [Member] \| Minimum [Member] \| Non Employee Director [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period			1 year
Performance Based Restricted Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting maximum number of annual installments \| Installment	3		3
2019 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock options authorized under plan	9,626,451		9,626,451
Common stock options available for issuance	1,903,955		1,903,955		1,948,815
Stock option exercised			4,676
Options granted			1,277,771		4,137,750,000	514,710,000
Percentage of share increase			5.00%
2019 Plan [Member] \| Time Based Vesting Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period			3 years		3 years
Expiration period					10 years
Weighted average fair value granted \| $ / shares			$ 1.79	$ 2.19	$ 2.19	$ 1.89
Stock-based compensation \| $	$ 1,000,000.0	900,000	$ 3,000,000.0	$ 2,500,000	$ 3,400,000	$ 10,000.00
Unrecognized stock-based compensation expense \| $	5,100,000		$ 5,100,000		$ 6,400,000	$ 1,000,000.0
Unrecognized stock-based compensation expense, period			1 year 7 months 9 days		3 years
2019 Plan [Member] \| Time Based Vesting Stock Option [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period			10 years
2019 Plan [Member] \| Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation \| $	$ 0	$ 0	$ 0	$ 0	$ 0
2016 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted						67,050
2016 Plan [Member] \| Time Based Vesting Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period					5 years
Expiration period					10 years
Weighted average fair value granted \| $ / shares						$ 37.16
Stock-based compensation \| $						$ 2,300,000