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CONVERTIBLE PREFERRED STOCK AND COMMON STOCK - Schedule of Convertible Preferred Stock (Details) - USD ($) $ in Thousands | Mar. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
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Class of Stock [Line Items] |  |  |  |
Convertible preferred stock, shares authorized | 409,351,021 | 409,351,021 | 321,346,716 |
Convertible preferred stock, shares outstanding | 175,528,225 | 175,437,783 | 191,139,933 | 186,466,181
Convertible preferred stock, $0.00001 par value; 409,351,021 and 321,346,716 shares authorized as of December 31, 2020 and 2019, respectively; 175,437,783 and 191,139,933 shares issued and outstanding as of December 31, 2020 and 2019, respectively; (liquidation preference of $257,947 and $258,041 as of December 31, 2020 and 2019, respectively) | $ 220,955 | $ 220,563 | $ 231,129 | $ 218,931
Convertible preferred stock, liquidation preference | $ 258,084 | $ 257,947 | $ 258,041 |
Series 1 convertible preferred stock, 4,305 shares authorized | 4,305 | 4,305 | 4,305 |
Series 1 convertible preferred stock, shares outstanding | 2,961 | 2,961 | 2,961 |
Authorized Shares (in shares) | 409,351,021 |  |  |
Outstanding Shares (in shares) | 175,531,186 |  |  |
Series D' |  |  |  |
Class of Stock [Line Items] |  |  |  |
Convertible preferred stock, shares authorized | 190,000,000 | 190,000,000 | 102,000,000 |
Convertible preferred stock, shares outstanding | 105,386,149 | 105,386,149 | 78,932,752 |
Convertible preferred stock, $0.00001 par value; 409,351,021 and 321,346,716 shares authorized as of December 31, 2020 and 2019, respectively; 175,437,783 and 191,139,933 shares issued and outstanding as of December 31, 2020 and 2019, respectively; (liquidation preference of $257,947 and $258,041 as of December 31, 2020 and 2019, respectively) | $ 129,339 |  |  |
Convertible preferred stock, liquidation preference | $ 161,515 | $ 161,516 | $ 120,972 |
Series D |  |  |  |
Class of Stock [Line Items] |  |  |  |
Convertible preferred stock, shares authorized | 87,235,535 | 87,235,535 | 87,235,535 |
Convertible preferred stock, shares outstanding | 33,483,143 | 33,392,701 | 35,586,652 |
Convertible preferred stock, $0.00001 par value; 409,351,021 and 321,346,716 shares authorized as of December 31, 2020 and 2019, respectively; 175,437,783 and 191,139,933 shares issued and outstanding as of December 31, 2020 and 2019, respectively; (liquidation preference of $257,947 and $258,041 as of December 31, 2020 and 2019, respectively) | $ 46,979 |  |  |
Convertible preferred stock, liquidation preference | $ 51,316 | $ 51,178 | $ 54,540 |
Series C |  |  |  |
Class of Stock [Line Items] |  |  |  |
Convertible preferred stock, shares authorized | 64,129,209 |  |  |
Convertible preferred stock, shares outstanding | 23,298,388 |  |  |
Convertible preferred stock, $0.00001 par value; 409,351,021 and 321,346,716 shares authorized as of December 31, 2020 and 2019, respectively; 175,437,783 and 191,139,933 shares issued and outstanding as of December 31, 2020 and 2019, respectively; (liquidation preference of $257,947 and $258,041 as of December 31, 2020 and 2019, respectively) | $ 35,293 |  |  |
Convertible preferred stock, liquidation preference | $ 35,514 |  |  |
Series B |  |  |  |
Class of Stock [Line Items] |  |  |  |
Convertible preferred stock, shares authorized | 36,969,407 | 36,969,407 | 36,969,407 |
Convertible preferred stock, shares outstanding | 9,185,302 | 9,185,302 | 9,126,596 |
Convertible preferred stock, $0.00001 par value; 409,351,021 and 321,346,716 shares authorized as of December 31, 2020 and 2019, respectively; 175,437,783 and 191,139,933 shares issued and outstanding as of December 31, 2020 and 2019, respectively; (liquidation preference of $257,947 and $258,041 as of December 31, 2020 and 2019, respectively) | $ 7,049 |  |  |
Convertible preferred stock, liquidation preference | $ 7,123 | $ 7,123 | $ 7,078 |
Series A' |  |  |  |
Class of Stock [Line Items] |  |  |  |
Convertible preferred stock, shares authorized | 30,991,277 |  |  |
Convertible preferred stock, shares outstanding | 4,158,503 |  |  |
Convertible preferred stock, $0.00001 par value; 409,351,021 and 321,346,716 shares authorized as of December 31, 2020 and 2019, respectively; 175,437,783 and 191,139,933 shares issued and outstanding as of December 31, 2020 and 2019, respectively; (liquidation preference of $257,947 and $258,041 as of December 31, 2020 and 2019, respectively) | $ 1,702 |  |  |
Convertible preferred stock, liquidation preference | $ 1,865 |  |  |
Series A |  |  |  |
Class of Stock [Line Items] |  |  |  |
Convertible preferred stock, shares authorized | 21,288 |  |  |
Convertible preferred stock, shares outstanding | 16,740 |  |  |
Convertible preferred stock, $0.00001 par value; 409,351,021 and 321,346,716 shares authorized as of December 31, 2020 and 2019, respectively; 175,437,783 and 191,139,933 shares issued and outstanding as of December 31, 2020 and 2019, respectively; (liquidation preference of $257,947 and $258,041 as of December 31, 2020 and 2019, respectively) | $ 593 |  |  |
Convertible preferred stock, liquidation preference | $ 751 |  |  |
Series 1 |  |  |  |
Class of Stock [Line Items] |  |  |  |
Convertible preferred stock, shares authorized |  | 4,305 | 4,305 |
Convertible preferred stock, shares outstanding |  | 2,961 | 2,961 |
Series 1 convertible preferred stock, 4,305 shares authorized | 4,305 |  |  |
Series 1 convertible preferred stock, shares outstanding | 2,961 |  |  |

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- Definition 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. + References No definition available. + Details
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- Definition 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. + References No definition available. + Details
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