REVERSE RECAPITALIZATION- Narrative (Details) $ / shares in Units, $ in Thousands		9 Months Ended
	Jul. 23, 2021 USD ($) $ / shares shares	Sep. 30, 2021 USD ($) shares		Sep. 30, 2020 USD ($) shares		Jul. 22, 2021 USD ($) shares	Jun. 30, 2021 shares	[1]	Dec. 31, 2020 USD ($) shares		Jun. 30, 2020 shares	[1]	Dec. 31, 2019 USD ($) shares
Schedule Of Reverse Recapitalization [Line Items]
Common stock, shares outstanding (in shares)	1,618,621,534	1,641,642,816				451,295,965			28,791,702
Share conversion deemed value (in dollars per share) | $ / shares	$ 10.00
Recapitalization exchange ratio	2.644
Stock converted, reverse recapitalization (in shares)	1,193,226,511
Equity awards outstanding (in shares)						42,182,931
Equity awards converted (in shares)	111,531,080
Convertible preferred stock, shares outstanding (in shares)		0	[1]	825,191,683	[1]	437,182,072	1,155,909,367		957,159,704	[1]	667,574,747		502,582,534	[1]
Options outstanding (in shares)		67,013,622				25,764,610			70,675,318
Options converted (in shares)	68,121,210
Non-option equity awards outstanding (in shares)						16,418,321
Non-option equity awards converted (in shares)	43,409,870
Proceeds from PIPE investment | $	$ 2,500,000
Working capital loan converted, amount | $	$ 1,500
Warrants issued for conversion of debt (in shares)	1,500,000
Price per warrant for warrants issued for conversion of debt (in dollars per share) | $ / shares	$ 1.00
Sponsor earnback shares (in shares)	17,250,000
Sponsor earnback warrants (in shares)	14,783,333
Proceeds from the reverse recapitalization | $	$ 4,439,200	$ 4,439,153		$ 0
Cash received upon completion of merger | $	2,070,100
Cash | $		$ 4,796,880		$ 512,675		$ 400			$ 614,412				$ 351,684
Payments for repurchase of common stock | $	$ 200
Shares repurchased (in shares)	21,644
Reverse recapitalization, transaction costs incurred | $	$ 38,900
Reverse recapitalizations, reduction to additional paid-in capital | $	36,200
Transaction costs expensed | $	2,700
Proceeds from reverse recapitalization, net of transaction costs | $	$ 4,400,300
Churchill
Schedule Of Reverse Recapitalization [Line Items]
Common stock, shares outstanding (in shares)						207,000,000
Stock repurchased during period, shares (in shares)	21,644
Stock repurchased during period, value | $	$ 200
Reverse recapitalization transaction costs paid to date | $						$ 131,400
Legacy Common Shareholders
Schedule Of Reverse Recapitalization [Line Items]
Stock converted, reverse recapitalization (in shares)	1,193,226,511
Legacy Preferred Shareholders
Schedule Of Reverse Recapitalization [Line Items]
Stock converted, reverse recapitalization (in shares)	437,182,072
PIPE Investors
Schedule Of Reverse Recapitalization [Line Items]
Shares outstanding prior to merger (in shares)	166,666,667
Preferred stock, price (in dollars per share) | $ / shares	$ 15.00

[1] The number of shares of convertible preferred stock and common stock issued and outstanding prior to the Merger have been retroactively adjusted by the Exchange Ratio to give effect to the reverse recapitalization treatment of the Merger. See Note 1 - Description of Business and Note 3 - Reverse Capitalization for more information.