MEZZANINE EQUITY, COMMON STOCK AND STOCKHOLDERS' (DEFICIT) EQUITY - SCHEDULE OF REDEEMABLE CONVERTIBLE PREFERRED STOCK (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Temporary Equity [Line Items]
Shares Authorized (in shares)	0	414,033,220
Shares issued (in shares)	0	412,742,897
Shares outstanding (in shares)	0	412,742,897
Liquidation Amount		$ 2,191,086,000
Carrying Value of Stock, Net of Issuance Costs	$ 0	$ 2,179,739,000
Unrecognized compensation cost	$ 2,170,000,000
Series A
Temporary Equity [Line Items]
Shares Authorized (in shares)		131,913,460
Shares issued (in shares)		131,913,460
Shares outstanding (in shares)		131,913,460
Per Share Liquidation Preference (in dollars per share)		$ 0.1954
Liquidation Amount		$ 25,777,000
Per Share Initial Conversion Price (in dollars per share)		$ 0.1954
Carrying Value of Stock, Net of Issuance Costs		$ 16,139,000
Series B
Temporary Equity [Line Items]
Shares Authorized (in shares)		80,263,020
Shares issued (in shares)		80,263,020
Shares outstanding (in shares)		80,263,020
Per Share Liquidation Preference (in dollars per share)		$ 0.6354
Liquidation Amount		$ 50,999,000
Per Share Initial Conversion Price (in dollars per share)		$ 0.6354
Carrying Value of Stock, Net of Issuance Costs		$ 50,999,000
Series C
Temporary Equity [Line Items]
Shares Authorized (in shares)		43,788,180
Shares issued (in shares)		43,788,180
Shares outstanding (in shares)		43,788,180
Per Share Liquidation Preference (in dollars per share)		$ 2.5121
Liquidation Amount		$ 110,000,000
Per Share Initial Conversion Price (in dollars per share)		$ 2.5121
Carrying Value of Stock, Net of Issuance Costs		$ 109,870,000
Series D
Temporary Equity [Line Items]
Shares Authorized (in shares)		35,774,761
Shares issued (in shares)		35,774,761
Shares outstanding (in shares)		35,774,761
Per Share Liquidation Preference (in dollars per share)		$ 10.1450
Liquidation Amount		$ 362,935,000
Per Share Initial Conversion Price (in dollars per share)		$ 10.1450
Carrying Value of Stock, Net of Issuance Costs		$ 362,670,000
Series E
Temporary Equity [Line Items]
Shares Authorized (in shares)		29,887,357
Shares issued (in shares)		29,887,357
Shares outstanding (in shares)		29,887,357
Per Share Liquidation Preference (in dollars per share)		$ 12.4827
Liquidation Amount		$ 373,075,000
Per Share Initial Conversion Price (in dollars per share)		$ 12.4827
Carrying Value of Stock, Net of Issuance Costs		$ 372,733,000
Series F
Temporary Equity [Line Items]
Shares Authorized (in shares)		48,000,000
Shares issued (in shares)		48,000,000
Shares outstanding (in shares)		48,000,000
Per Share Liquidation Preference (in dollars per share)		$ 12.5000
Liquidation Amount		$ 600,000,000
Per Share Initial Conversion Price (in dollars per share)		$ 12.5000
Carrying Value of Stock, Net of Issuance Costs		$ 599,284,000
Series G
Temporary Equity [Line Items]
Shares Authorized (in shares)		44,406,442
Shares issued (in shares)		43,116,119
Shares outstanding (in shares)		43,116,119
Per Share Liquidation Preference (in dollars per share)		$ 15.5000
Liquidation Amount		$ 668,300,000
Per Share Initial Conversion Price (in dollars per share)		$ 15.5000
Carrying Value of Stock, Net of Issuance Costs		$ 668,044,000

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

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Carrying amount, attributable to parent, of an entity's issued and outstanding stock which is not included within permanent equity. 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. Includes stock with a put option held by an ESOP and stock redeemable by a holder only in the event of a change in control of the issuer.

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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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The aggregate liquidation preference (or restrictions) of stock classified as temporary equity that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share. 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.

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The per share liquidation preference (or restrictions) of stock classified as temporary equity that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share. 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.

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Amount to be paid per share that is classified as temporary equity by entity upon redemption. 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.

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The maximum number of securities classified as temporary equity that are permitted to be issued by an entity's charter and bylaws. 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.

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The number of securities classified as temporary equity that have been sold (or granted) to the entity's shareholders. Securities issued include securities outstanding and 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.

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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.

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