SUPPLEMENTAL CASH FLOW INFORMATION (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018
Supplemental Cash Flow Information [Abstract]
Cash (paid) for interest, net of amount capitalized	$ (30.4)	$ (26.1)
Cash (paid) for income taxes, net	(9.4)	(8.6)
Significant non-cash investing and financing transactions
Accounts payable related to construction costs	31.3	13.0
Accounts payable related to the transfer of certain software assets from affiliates	$ 0.0	$ 5.5

Future cash outflow to pay for purchases of fixed assets that have occurred.

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