Supplemental Cash Flow Information - Supplemental Information (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplemental cash flow information
Cash paid for interest, net of amount capitalized	$ 485.9	$ 441.5	$ 413.7
Cash paid (received) for income taxes, net	(24.9)	16.3	(5.2)
Accounts payable related to construction costs	159.9	65.9	169.2
Capital contributions from noncontrolling interest	21.0	0.0	0.0
Receivable related to corporate-owned life insurance proceeds	0.0	7.7	0.0
Bostco
Supplemental cash flow information
Portion of Bostco real estate holdings sale financed with note receivable	$ 0.0	$ 0.0	$ 7.0

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

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