Financial Information for Subsidiary and Guarantor Parent (B.S.) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 229.6	$ 149.8	$ 269.5	$ 1,026.8
Accounts receivable, net	452.1	400.3
Intercompany notes receivable	0.0	0.0
Inventories, net	1,037.0	1,271.6
Prepaid expenses and other current assets	47.8	45.9
Total Current Assets	1,766.5	1,867.6
Property, plant and equipment, net	2,498.9	2,928.2
Goodwill	641.9	651.4
Intercompany notes receivable	0.0	0.0
Investments in subsidiaries	0.0	0.0
Other assets	262.7	304.5
Total Assets	5,170.0	5,751.7	6,571.7
Accounts payable	294.3	380.8
Accrued liabilities	309.3	301.8
Intercompany notes payable	0.0	0.0
Short-term debt and current portion of long-term debt	105.1	3.9
Total Current Liabilities	708.7	686.5
Long-term debt	1,771.9	1,491.8
Intercompany notes payable	0.0	0.0
Accrued postretirement benefits	317.7	359.2
Pension liabilities	827.9	833.8
Deferred income taxes	15.6	75.6
Other long-term liabilities	83.4	108.3
Total Liabilities	3,725.2	3,555.2
Redeemable noncontrolling interest	0.0	12.1
Total Stockholders’ Equity	1,444.8	2,184.4	$ 2,709.3	$ 2,994.7
Total Liabilities and Stockholders’ Equity	5,170.0	5,751.7
Legal Entities [Member] | Guarantor Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	2.3	0.4
Accounts receivable, net	0.1	0.1
Intercompany notes receivable	0.0	0.0
Inventories, net	0.0	0.0
Prepaid expenses and other current assets	6.6	9.3
Total Current Assets	9.0	9.8
Property, plant and equipment, net	1.3	2.2
Goodwill	0.0	0.0
Intercompany notes receivable	0.0	0.0
Investments in subsidiaries	5,241.2	5,742.5
Other assets	23.0	13.4
Total Assets	5,274.5	5,767.9
Accounts payable	3.1	4.8
Accrued liabilities	54.6	42.1
Intercompany notes payable	1,341.1	1,325.4
Short-term debt and current portion of long-term debt	0.4	0.7
Total Current Liabilities	1,399.2	1,373.0
Long-term debt	1,621.7	1,341.7
Intercompany notes payable	0.0	0.0
Accrued postretirement benefits	0.0	0.0
Pension liabilities	778.5	778.0
Deferred income taxes	15.6	75.6
Other long-term liabilities	14.7	15.2
Total Liabilities	3,829.7	3,583.5
Redeemable noncontrolling interest		0.0
Total Stockholders’ Equity	1,444.8	2,184.4
Total Liabilities and Stockholders’ Equity	5,274.5	5,767.9
Legal Entities [Member] | Subsidiary [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	2.5	2.8
Accounts receivable, net	107.8	100.3
Intercompany notes receivable	0.0	0.0
Inventories, net	106.7	239.9
Prepaid expenses and other current assets	5.2	3.8
Total Current Assets	222.2	346.8
Property, plant and equipment, net	1,583.6	1,559.9
Goodwill	0.0	0.0
Intercompany notes receivable	0.0	0.0
Investments in subsidiaries	37.7	37.7
Other assets	25.5	23.0
Total Assets	1,869.0	1,967.4
Accounts payable	97.4	171.1
Accrued liabilities	83.3	74.0
Intercompany notes payable	1,551.8	1,276.1
Short-term debt and current portion of long-term debt	0.3	0.1
Total Current Liabilities	1,732.8	1,521.3
Long-term debt	150.0	149.7
Intercompany notes payable	200.0	200.0
Accrued postretirement benefits	244.0	280.0
Pension liabilities	5.2	5.2
Deferred income taxes	0.0	0.0
Other long-term liabilities	18.1	20.7
Total Liabilities	2,350.1	2,176.9
Redeemable noncontrolling interest		0.0
Total Stockholders’ Equity	(481.1)	(209.5)
Total Liabilities and Stockholders’ Equity	1,869.0	1,967.4
Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	224.8	146.6
Accounts receivable, net	344.2	299.9
Intercompany notes receivable	2,892.9	2,601.5
Inventories, net	930.3	1,031.7
Prepaid expenses and other current assets	36.0	32.8
Total Current Assets	4,428.2	4,112.5
Property, plant and equipment, net	914.0	1,366.1
Goodwill	641.9	651.4
Intercompany notes receivable	200.0	200.0
Investments in subsidiaries	0.0	0.0
Other assets	214.2	268.1
Total Assets	6,398.3	6,598.1
Accounts payable	193.8	204.9
Accrued liabilities	171.4	185.7
Intercompany notes payable	0.0	0.0
Short-term debt and current portion of long-term debt	104.4	3.1
Total Current Liabilities	469.6	393.7
Long-term debt	0.2	0.4
Intercompany notes payable	0.0	0.0
Accrued postretirement benefits	73.7	79.2
Pension liabilities	44.2	50.6
Deferred income taxes	0.0	0.0
Other long-term liabilities	50.6	72.4
Total Liabilities	638.3	596.3
Redeemable noncontrolling interest		12.1
Total Stockholders’ Equity	5,760.0	5,989.7
Total Liabilities and Stockholders’ Equity	6,398.3	6,598.1
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0.0	0.0
Accounts receivable, net	0.0	0.0
Intercompany notes receivable	(2,892.9)	(2,601.5)
Inventories, net	0.0	0.0
Prepaid expenses and other current assets	0.0	0.0
Total Current Assets	(2,892.9)	(2,601.5)
Property, plant and equipment, net	0.0	0.0
Goodwill	0.0	0.0
Intercompany notes receivable	(200.0)	(200.0)
Investments in subsidiaries	(5,278.9)	(5,780.2)
Other assets	0.0	0.0
Total Assets	(8,371.8)	(8,581.7)
Accounts payable	0.0	0.0
Accrued liabilities	0.0	0.0
Intercompany notes payable	(2,892.9)	(2,601.5)
Short-term debt and current portion of long-term debt	0.0	0.0
Total Current Liabilities	(2,892.9)	(2,601.5)
Long-term debt	0.0	0.0
Intercompany notes payable	(200.0)	(200.0)
Accrued postretirement benefits	0.0	0.0
Pension liabilities	0.0	0.0
Deferred income taxes	0.0	0.0
Other long-term liabilities	0.0	0.0
Total Liabilities	(3,092.9)	(2,801.5)
Redeemable noncontrolling interest		0.0
Total Stockholders’ Equity	(5,278.9)	(5,780.2)
Total Liabilities and Stockholders’ Equity	$ (8,371.8)	$ (8,581.7)