INCOME TAXES - Effective Income Tax Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Loss before income taxes	$ (521.1)	$ (363.0)	$ (282.4)
Amount
Statutory U.S. federal income tax benefit	(109.4)	(76.2)	(59.3)
Valuation allowance on deferred tax assets	116.7	61.5	57.4
Warrants fair value adjustment	0.0	11.5	0.0
Share-based compensation	(3.3)	5.0	1.7
Nondeductible compensation	1.8	0.0	0.0
State net operating loss	(4.9)	(3.1)	(2.2)
Other	(0.9)	1.3	2.4
Total income tax expense (benefit)	$ 0.0	$ 0.0	$ 0.0
Percent
Statutory U.S. federal income tax benefit	21.00%	21.00%	21.00%
Valuation allowance on deferred tax assets	(22.40%)	(16.90%)	(20.30%)
Warrants fair value adjustment	0.00%	(3.20%)	0.00%
Share-based compensation	0.60%	(1.40%)	(0.60%)
Nondeductible compensation	(0.30%)	0.00%	0.00%
State net operating loss	0.90%	0.90%	0.80%
Other	0.20%	(0.40%)	(0.90%)
Income tax expense (benefit)	0.00%	0.00%	0.00%

Effective Income Tax, Operating Loss Carryforwards, State And Local, Amount

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