REVENUE - Contract Balances (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Contract assets	$ 1,027.0		$ 1,027.0		$ 886.8
Contract (liabilities)	(914.6)		(914.6)		(1,046.8)
Net contract assets (liabilities)	112.4		112.4		$ (160.0)
Contract assets, increase (decrease)			$ 140.2
Contract with customer, asset, net, current, increase (decrease), (in percent)			15.80%
Contract (liabilities), (increase) decrease			$ 132.2
Contract with customer liability, current, increase (decrease), (in percent)			12.60%
Net contract assets (liabilities), increase (decrease)			$ 272.4
Contract assets (liabilities), current, net, increase (decrease), (in percent)			170.30%
Contract with customer, liability, revenue recognized	53.4	$ 69.7	$ 250.5	$ 424.1
Contract with customer, performance obligation satisfied in previous period	$ 4.3	$ (2.3)	$ 6.9	$ (17.2)