Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Accounts payable and accrued expenses [Line Items]
Trade accounts payable	$ 254.8	$ 281.7
Accrued payroll and related benefits	186.2	209.3
Other accrued expenses	118.5	184.9
Accrued taxes other than income	99.0	111.4
Liabilities associated with discontinued operations	98.2	63.8
Accrued royalties	61.7	52.7
Liabilities associated with discontinued operations	58.8	54.0
Operating lease liabilities	29.6	0.0
Workers’ compensation obligations	15.8	10.0
Accrued interest	15.0	15.7
Income taxes payable	8.4	7.0
Intangible take-or-pay contracts	8.4	20.3
Income taxes payable	2.6	10.0
Liabilities from coal trading activities	0.0	1.2
Accounts payable and accrued expenses	$ 957.0	$ 1,022.0