Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Accumulated other comprehensive income [Line Items]
Foreign Currency Translation Adjustment		$ (142.7)		$ (148.2)
Foreign Currency Translation Adjustment, Reclassification from other comprehensive income to earnings		0.0
Foreign Currency Translation Adjustment, Current period change		5.5	$ 2.7
Net Actuarial Loss Associated With Postretirement Plans And Workers' Compensation Obligation		(250.5)		(256.3)
Net actuarial loss associated with postretirement plans and workers' compensation obligations, Reclassification from other comprehensive income to earnings	[1]	5.8	5.2
Net actuarial loss associated with postretirement plans and workers' compensation obligations, Current period change		0.0
Prior Service Cost Associated with Postretirement Plans		20.3		21.7
Prior service cost associated with postretirement plans, Reclassification from other comprehensive income to earnings	[1]	(1.4)	(1.6)
Prior service cost associated with postretirement plans, Current period change		0.0
Cash Flow Hedges		(75.6)		(94.2)
Cash flow hedges, Reclassification from other comprehensive income to earnings	[1]	18.6	49.7
Cash flow hedges, Current period change		0.0
Total Accumulated Other Comprehensive Loss		(448.5)		$ (477.0)
Total Accumulated Other Comprehensive Loss, Reclassification from other comprehensive income to earnings		23.0
Total Accumulated Other Comprehensive Loss, Current period change		5.5
PostretirementHealthCareAndLifeInsuranceBenefitsOperatingCostsAndExpensesActuarialLoss [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	[1]	(5.5)	(5.1)
DefinedBenefitPensionPlansOperatingCostsAndExpensesActuarialLoss [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	[1]	(5.3)	(5.1)
DefinedBenefitPensionPlansSellingAndAdministrativeExpensesActuarialLoss [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	[1]	(1.0)	(1.0)
InsignificantItemsActuarialLoss [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	[1]	2.7	2.9
NetActuarialLossAssociatedWithPostretirementPlansAndWorkersCompensationObligationsTotalBeforeIncomeTaxes [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	[1]	(9.1)	(8.3)
IncomeTaxProvisionActuarialLoss [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, Tax	[1]	3.3	3.1
PostretirementHealthCareAndLifeInsuranceBenefitsOperatingCostsAndExpensesPriorServiceCost [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax	[1]	2.3	2.7
Definedbenefitpensionplanspriorservicecost [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax	[1]	(0.1)	(0.1)
PriorServiceCostAssociatedWithPostretirementPlansAndWorkersCompensationObligationsTotalBeforeIncomeTaxes [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax	[1]	2.2	2.6
Incometaxprovisionpriorservicecost [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, Tax	[1]	(0.8)	(1.0)
ForeignCurrencyCashFlowHedgeContractsOperatingCostsAndExpenses [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	[1]	(16.6)	(53.9)
CommoditySwapsOperatingCostsAndExpenses [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	[1]	(11.0)	(24.8)
CoalTradingOtherRevenues [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	[1]	0.0	0.0
InsignificantItemsCashFlowHedges [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	[1]	(0.1)	(0.2)
TotalBeforeIncomeTaxesCashFlowHedges [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	[1]	(27.7)	(78.9)
IncomeTaxProvisionCashFlowHedges [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	[1]	$ 9.1	$ 29.2

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