CONTINGENTLY REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY Contingently Redeemable Preferred Stock (Details) - USD ($) $ in Millions	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Shares authorized (in shares)	579,587,560			508,054,624
Shares outstanding (in shares)	575,864,510	576,000,000	576,000,000	503,951,340	504,000,000	343,000,000	343,000,000	343,000,000
Carrying Value	$ 7,894	$ 7,894	$ 7,894	$ 5,244	$ 5,250	$ 2,750	$ 2,750	$ 2,750
Liquidation Value	$ 7,894			$ 5,244
Common Stock Issuable Upon Conversion	575,864,510			503,951,340
Series A
Class of Stock [Line Items]
Shares authorized (in shares)	117,527,250			117,527,250
Shares outstanding (in shares)	117,527,250			117,527,250
Carrying Value	$ 600			$ 600
Liquidation Value	$ 600			$ 600
Common Stock Issuable Upon Conversion	117,527,250			117,527,250
Series B
Class of Stock [Line Items]
Shares authorized (in shares)	65,904,000			65,904,000
Shares outstanding (in shares)	65,904,000			65,904,000
Carrying Value	$ 500			$ 500
Liquidation Value	$ 500			$ 500
Common Stock Issuable Upon Conversion	65,904,000			65,904,000
Series C
Class of Stock [Line Items]
Shares authorized (in shares)	42,231,150			42,231,150
Shares outstanding (in shares)	38,508,100			38,508,100
Carrying Value	$ 350			$ 350
Liquidation Value	$ 350			$ 350
Common Stock Issuable Upon Conversion	38,508,100			38,508,100
Series D
Class of Stock [Line Items]
Shares authorized (in shares)	120,836,866			120,997,772
Shares outstanding (in shares)	120,836,866			120,836,866
Carrying Value	$ 1,297			$ 1,297
Liquidation Value	$ 1,297			$ 1,297
Common Stock Issuable Upon Conversion	120,836,866			120,836,866
Series E
Class of Stock [Line Items]
Shares authorized (in shares)	161,175,124			161,394,452
Shares outstanding (in shares)	161,175,124			161,175,124
Carrying Value	$ 2,497			$ 2,497
Liquidation Value	$ 2,497			$ 2,497
Common Stock Issuable Upon Conversion	161,175,124			161,175,124
Series F
Class of Stock [Line Items]
Shares authorized (in shares)	71,913,170
Shares outstanding (in shares)	71,913,170
Carrying Value	$ 2,650
Liquidation Value	$ 2,650
Common Stock Issuable Upon Conversion	71,913,170