Employee Benefits Employee Benefits, Defined Benefit Plans Narrative (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) trustrees	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Mar. 31, 2016 USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accrued Annual Veba Contribution		$ 20,000,000	$ 19,600,000
Long-term portion of contingent contribution to Union VEBA		12,800,000	29,900,000
Defined Benefit Plan, Fair Value of Plan Assets		69,600,000	69,100,000
(Gain) loss on removal of Union VEBA net assets – Note 6		(100,000)	493,400,000	$ 0
Canadian pension plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Benefit Obligation		7,000,000	6,100,000	7,000,000
Defined Benefit Plan, Fair Value of Plan Assets		6,100,000	5,700,000	6,300,000
Defined Benefit Plan, Accumulated Benefit Obligation		6,400,000	5,400,000
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year		$ 400,000
Union VEBA
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of Trustees | trustrees		4
Percent allocation of total contribution between VEBAs		85.50%
Accrued Annual Veba Contribution		$ 17,100,000	16,800,000		$ 16,700,000
Long-term portion of contingent contribution to Union VEBA		$ 12,800,000
Accrued Veba contingent contribution - total	$ 46,700,000
Loss on settlement of Union VEBA - net of tax	307,800,000
Income tax benefit on removal of Union VEBA net assets	$ 184,400,000
Salaried VEBA
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percent allocation of total contribution between VEBAs		14.50%
Accrued Annual Veba Contribution		$ 2,900,000	2,800,000
Defined Benefit Plan, Future Amortization of Prior Service Cost (Credit)		4,000,000
Defined Benefit Plan, Amount to be Amortized from Accumulated Other Comprehensive Income (Loss) Next Fiscal Year		4,500,000
Defined Benefit Plan, Future Amortization of Gain (Loss)		500,000
VEBAs
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Cash flow in determining VEBA obligation		20,000,000
Minimum liquidity requirement in determining VEBA obligation		50,000,000
Defined Benefit Plan, Benefit Obligation		86,800,000	77,900,000	470,900,000
Defined Benefit Plan, Fair Value of Plan Assets		$ 58,200,000	$ 58,900,000	$ 793,800,000
Fixed Income Securities | London Ontario Facility | Canadian pension plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations		32.00%
Defined Benefit Plan, Target Plan Asset Allocations		30.00%
Equity Securities | London Ontario Facility | Canadian pension plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations		63.00%
Defined Benefit Plan, Target Plan Asset Allocations		65.00%
Company Appointed | Union VEBA
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of Trustees | trustrees		2
Usw Appointed | Union VEBA
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of Trustees | trustrees		2
Annual Cash Flows up to $20 Million | VEBAs
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Postretirement Medical Plan Contribution Obligation Percentage		10.00%
Annual Cash Flows in Excess of $20 Million | VEBAs
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Postretirement Medical Plan Contribution Obligation Percentage		20.00%
Maximum | VEBAs
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Postretirement Medical Plan Contribution Obligation		$ 20,000,000
Variable cash contribution | VEBAs
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Annual VEBA contribution paid		$ 19,500,000