REVENUE - Contract Balances (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Contract assets	$ 928.3		$ 928.3		$ 886.8
Contract (liabilities)	(833.6)		(833.6)		(1,046.8)
Net contract assets (liabilities)	94.7		94.7		$ (160.0)
Contract assets, increase (decrease)			$ 41.5
Contract with customer, asset, net, current, increase (decrease), (in percent)			4.70%
Contract (liabilities), (increase) decrease			$ 213.2
Contract with customer liability, current, increase (decrease), (in percent)			20.40%
Net contract assets (liabilities), increase (decrease)			$ 254.7
Contract assets (liabilities), current, net, increase (decrease), (in percent)			159.20%
Contract with customer, liability, revenue recognized	68.7	$ 211.0	$ 197.1	$ 354.4
Contract with customer, performance obligation satisfied in previous period	$ 7.9	$ (3.1)	$ 2.6	$ (14.9)