Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	$ 36.4	$ 88.2
Increase Decrease in Capital Expenditures Incurred But Not Yet Paid	(29.8)	63.2	$ (96.8)
Cash paid (received) during the period for:
Interest	232.8	231.3	196.0
Less amount capitalized	33.3	28.5	22.1
Cash interest, net	199.5	202.8	173.9
Income taxes	6.2	46.5	(34.2)
Dividends payable		20.0	11.8
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	36.4	88.2
Depreciation	846.4	877.6	878.2
Amortization of Intangible Assets	$ 1.2	$ 5.1	$ 5.7
Gulf Sulphur Services
Cash paid (received) during the period for:
Equity method investment, ownership percentage	50.00%