Mezzanine Equity and Stockholders' Deficiency - Summary of Redeemable Convertible Preferred Stock (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Temporary Equity [Line Items]
Shares issued	4,832,409	4,832,409	5,878,352
Shares outstanding	4,832,409	4,832,409	5,878,352
Liquidation preference	$ 400,317	$ 403,361	$ 281,900
Recorded amount	$ 192,184	$ 183,390	$ 182,656
Series B-1 Preferred Stock [Member]
Temporary Equity [Line Items]
Shares issued			694,498
Shares outstanding			694,498
Liquidation preference			$ 22,841
Recorded amount			$ 21,456
Series B-2 Preferred Stock [Member]
Temporary Equity [Line Items]
Shares issued			351,445
Shares outstanding			351,445
Liquidation preference			$ 11,559
Recorded amount			$ 10,858
Series C Preferred Stock [Member]
Temporary Equity [Line Items]
Shares issued	4,832,409	4,832,409	4,832,409
Shares outstanding	4,832,409	4,832,409	4,832,409
Liquidation preference	$ 400,300	$ 403,361	$ 247,500
Recorded amount		$ 183,390	$ 150,342

The number of securities classified as temporary equity that have been issued and are held by the entity's shareholders. Securities outstanding equals securities issued minus securities held in treasury. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(27)(b))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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Period Type:	instant