Employee Benefits Employee Benefits, Benefit obligations and funded status of our Canadian pension and the VEBAs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Change in plan assets:
Net Asset In Respect Of Vebas	$ 0.0	$ 340.1
Net liabilities of Salaried VEBA	19.0	17.2
Accrued Annual Veba Contribution	19.6	13.7
Union VEBA
Change in benefit obligation:
Obligation at beginning of year	391.5
Defined Benefit Plan, Settlements, Benefit Obligation	(391.5)
Obligation at end of year	0.0	391.5
Change in plan assets:
Fair value of plan assets at beginning of year	731.6
Defined Benefit Plan, Settlements, Plan Assets	(778.3)
Fair value of plan assets at end of year	0.0	731.6
Defined Benefit Plan, Funded Status of Plan	0.0	340.1
Prior Service Cost Due to a New Death Benefit		15.9
Actuarial (Gain) Loss Due To Change In Discount Rate		45.0
Actuarial (gain) loss due to changes in prescription drug claim costs and Retiree Drug Subsidy assumptions		(18.0)
Actuarial (Gain) Loss Due To Changes In Administrative Costs		0.4
Prior Service Cost Due to Increase in the Annual Healthcare Reimbursement		60.5
Accrued Veba contingent contribution - total	46.7
Accrued Annual Veba Contribution	16.8
Salaried VEBA
Change in benefit obligation:
Obligation at beginning of year	79.4
Obligation at end of year	77.9	79.4
Change in plan assets:
Fair value of plan assets at beginning of year	62.2
Fair value of plan assets at end of year	58.9	62.2
Defined Benefit Plan, Funded Status of Plan	(19.0)	(17.2)
Prior Service Cost resulting from a change in benefit cost for plan participants		14.0
Prior Service Cost Due to Increase in the Annual Healthcare Reimbursement	13.2
Accrued Annual Veba Contribution	2.8
VEBAs
Change in benefit obligation:
Obligation at beginning of year	470.9	374.7
Defined Benefit Plan, Foreign Currency Exchange Rate Gain (Loss)	0.0	0.0
Defined Benefit Plan, Service Cost	0.0	2.2
Defined Benefit Plan, Interest Cost	2.7	16.7
Defined Benefit Plan, Plan Amendments	13.2	90.4
Defined Benefit Plan, Actuarial Gain (Loss)	11.2	(10.2)
Benefits paid by VEBA	(6.2)	(24.7)
Defined Benefit Plan, Gross Prescription Drug Subsidy Receipts Received	0.0	1.4
Obligation at end of year	77.9	470.9
Change in plan assets:
Fair value of plan assets at beginning of year	793.8	780.7
Defined Benefit Plan, Actual Return on Plan Assets	0.1	22.7
Defined Benefit Plan, Contributions by Employer	49.5	13.7
Benefits paid by VEBA	(6.2)	(24.7)
Defined Benefit Plan, Gross Prescription Drug Subsidy Receipts Received	0.0	1.4
Fair value of plan assets at end of year	58.9	793.8
Defined Benefit Plan, Funded Status of Plan	(19.0)	322.9
Actuarial (gain) loss due to projected lower benefit utilization	5.5	53.6
Actuarial (Gain) Loss Due To Change In Discount Rate	(2.0)
Actuarial (Gain) Loss Due To Changes In Census Data	(3.7)	37.2
Canadian pension plan
Change in benefit obligation:
Obligation at beginning of year	7.0	6.6
Defined Benefit Plan, Foreign Currency Exchange Rate Gain (Loss)	(1.0)	(0.5)
Defined Benefit Plan, Service Cost at Balance Sheet Exchange Rate	0.2	0.2
Defined Benefit Plan, Interest Cost at Balance Sheet Exchange Rate	0.2	0.3
Defined Benefit Plan, Actuarial Gain (Loss)	0.1	(0.7)
Defined Benefit Plan, Benefits Paid	0.2	0.3
Obligation at end of year	6.1	7.0
Change in plan assets:
Fair value of plan assets at beginning of year	6.3	6.2
Defined Benefit Plan, Foreign Currency Exchange Rate Changes, Plan Assets	(1.0)	(0.5)
Defined Benefit Plan, Actual Return on Plan Assets	0.3	0.6
Defined Benefit Plan, Contributions by Employer	0.3	0.3
Defined Benefit Plan, Benefits Paid	0.2	0.3
Fair value of plan assets at end of year	5.7	6.3
Defined Benefit Plan, Funded Status of Plan	$ (0.4)	$ (0.7)