RECEIVABLES - Roll-forward of allowance for credit losses (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Contract assets
Allowance for credit losses at December 31, 2020	$ 2.4
Allowance for credit losses at September 30, 2021	1.2
Trade receivables
Trade receivables
Allowance for credit losses at December 31, 2020	40.2	$ 59.4
Current period provision (release) for expected credit losses	(0.7)	35.7
Recoveries	(1.2)	(6.2)
Allowance for credit losses at September 30, 2021	38.3	88.9
Contract assets
Contract assets
Allowance for credit losses at December 31, 2020	2.4	4.5
Current period provision (release) for expected credit losses	(0.5)	0.1
Recoveries	(0.7)	(2.8)
Allowance for credit losses at September 30, 2021	1.2	1.8
Loans receivable
Loans receivable
Allowance for credit losses at December 31, 2020	7.5	9.5
Current period provision (release) for expected credit losses	(0.1)	0.1
Recoveries	0.0	(0.6)
Allowance for credit losses at September 30, 2021	7.4	9.0
Security deposit and other
Security deposit and other
Allowance for credit losses at December 31, 2020	0.4	0.7
Current period provision (release) for expected credit losses	(0.1)	0.0
Recoveries	0.0	0.0
Allowance for credit losses at September 30, 2021	0.3	0.7
Held-to-maturity debt securities
Held-to-maturity debt securities
Allowance for credit losses at December 31, 2020	0.5	1.1
Current period provision (release) for expected credit losses	2.2	0.0
Recoveries	0.0	0.0
Allowance for credit losses at September 30, 2021	$ 2.7	$ 1.1