RECEIVABLES - Roll-forward of allowance for credit losses (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Contract assets
Beginning balance in allowance for credit losses	$ 2.4
Ending balance in the allowance for credit losses	0.2
Trade receivables
Trade receivables
Beginning balance in allowance for credit losses	40.2	$ 59.4
Current period provision (release) for expected credit losses	3.4	29.9
Recoveries	(0.1)	(3.2)
Ending balance in the allowance for credit losses	43.5	86.1
Contract assets
Contract assets
Beginning balance in allowance for credit losses	2.4	4.5
Current period provision (release) for expected credit losses	(0.6)	0.2
Recoveries	(1.6)	(2.7)
Ending balance in the allowance for credit losses	0.2	2.0
Loans receivable
Loans receivable
Beginning balance in allowance for credit losses	7.5	9.5
Current period provision (release) for expected credit losses	(0.7)	0.1
Recoveries	0.5	(0.6)
Ending balance in the allowance for credit losses	7.3	9.0
Security deposit and other
Security deposit and other
Beginning balance in allowance for credit losses	0.4	0.7
Current period provision (release) for expected credit losses	0.0	0.0
Recoveries	0.0	0.0
Ending balance in the allowance for credit losses	0.4	0.7
Held-to-maturity debt securities
Held-to-maturity debt securities
Beginning balance in allowance for credit losses	0.5	1.1
Current period provision (release) for expected credit losses	0.0	0.0
Recoveries	0.0	0.0
Ending balance in the allowance for credit losses	$ 0.5	$ 1.1