Financial Information for Subsidiary and Guarantor Parent (B.S.) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 149.8	$ 269.5	$ 1,026.8	$ 304.6
Accounts receivable, net	400.3	603.6
Intercompany notes receivable	0.0	0.0
Inventories, net	1,271.6	1,472.8
Prepaid expenses and other current assets	45.9	136.2
Total Current Assets	1,867.6	2,482.1
Property, plant and equipment, net	2,928.2	2,961.8
Goodwill	651.4	780.4
Intercompany notes receivable	0.0	0.0
Investments in subsidiaries	0.0	0.0
Other assets	304.5	347.4
Total Assets	5,751.7	6,571.7	6,885.0
Accounts payable	380.8	556.7
Accrued liabilities	301.8	323.2
Intercompany notes payable	0.0	0.0
Short-term debt and current portion of long-term debt	3.9	17.8
Total Current Liabilities	686.5	897.7
Long-term debt	1,491.8	1,498.2
Intercompany notes payable	0.0	0.0
Accrued postretirement benefits	359.2	415.8
Pension liabilities	833.8	739.3
Deferred income taxes	75.6	143.1
Other long-term liabilities	108.3	156.2
Total Liabilities	3,555.2	3,850.3
Redeemable noncontrolling interest	12.1	12.1
Total Stockholders’ Equity	2,184.4	2,709.3	$ 2,994.7	$ 2,587.1
Total Liabilities and Stockholders’ Equity	5,751.7	6,571.7
Guarantor Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0.4	2.2
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	9.3	63.7
Total Current Assets	9.8	66.0
Property, plant and equipment, net	2.2	2.2
Goodwill	0.0	0.0
Intercompany notes receivable	0.0	0.0
Investments in subsidiaries	5,742.5	6,149.4
Other assets	13.4	13.3
Total Assets	5,767.9	6,230.9
Accounts payable	4.8	4.5
Accrued liabilities	42.1	47.5
Intercompany notes payable	1,325.4	1,232.6
Short-term debt and current portion of long-term debt	0.7	0.5
Total Current Liabilities	1,373.0	1,285.1
Long-term debt	1,341.7	1,340.2
Intercompany notes payable	0.0	0.0
Accrued postretirement benefits	0.0	0.0
Pension liabilities	778.0	675.5
Deferred income taxes	75.6	143.1
Other long-term liabilities	15.2	77.7
Total Liabilities	3,583.5	3,521.6
Redeemable noncontrolling interest	0.0	0.0
Total Stockholders’ Equity	2,184.4	2,709.3
Total Liabilities and Stockholders’ Equity	5,767.9	6,230.9
Subsidiary [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	2.8	13.8
Accounts receivable, net	100.3	209.1
Intercompany notes receivable	0.0	0.0
Inventories, net	239.9	387.7
Prepaid expenses and other current assets	3.8	13.2
Total Current Assets	346.8	623.8
Property, plant and equipment, net	1,559.9	1,545.1
Goodwill	0.0	126.6
Intercompany notes receivable	0.0	0.0
Investments in subsidiaries	37.7	37.7
Other assets	23.0	27.5
Total Assets	1,967.4	2,360.7
Accounts payable	171.1	302.0
Accrued liabilities	74.0	72.0
Intercompany notes payable	1,276.1	1,158.2
Short-term debt and current portion of long-term debt	0.1	0.1
Total Current Liabilities	1,521.3	1,532.3
Long-term debt	149.7	149.8
Intercompany notes payable	200.0	200.0
Accrued postretirement benefits	280.0	153.0
Pension liabilities	5.2	6.0
Deferred income taxes	0.0	0.0
Other long-term liabilities	20.7	22.5
Total Liabilities	2,176.9	2,063.6
Redeemable noncontrolling interest	0.0	0.0
Total Stockholders’ Equity	(209.5)	297.1
Total Liabilities and Stockholders’ Equity	1,967.4	2,360.7
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	146.6	253.5
Accounts receivable, net	299.9	394.4
Intercompany notes receivable	2,601.5	2,390.8
Inventories, net	1,031.7	1,085.1
Prepaid expenses and other current assets	32.8	59.3
Total Current Assets	4,112.5	4,183.1
Property, plant and equipment, net	1,366.1	1,414.5
Goodwill	651.4	653.8
Intercompany notes receivable	200.0	200.0
Investments in subsidiaries	0.0	0.0
Other assets	268.1	306.6
Total Assets	6,598.1	6,758.0
Accounts payable	204.9	250.2
Accrued liabilities	185.7	203.7
Intercompany notes payable	0.0	0.0
Short-term debt and current portion of long-term debt	3.1	17.2
Total Current Liabilities	393.7	471.1
Long-term debt	0.4	8.2
Intercompany notes payable	0.0	0.0
Accrued postretirement benefits	79.2	262.8
Pension liabilities	50.6	57.8
Deferred income taxes	0.0	0.0
Other long-term liabilities	72.4	56.0
Total Liabilities	596.3	855.9
Redeemable noncontrolling interest	12.1	12.1
Total Stockholders’ Equity	5,989.7	5,890.0
Total Liabilities and Stockholders’ Equity	6,598.1	6,758.0
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	(2,601.5)	(2,390.8)
Inventories, net	0.0	0.0
Prepaid expenses and other current assets	0.0	0.0
Total Current Assets	(2,601.5)	(2,390.8)
Property, plant and equipment, net	0.0	0.0
Goodwill	0.0	0.0
Intercompany notes receivable	(200.0)	(200.0)
Investments in subsidiaries	(5,780.2)	(6,187.1)
Other assets	0.0	0.0
Total Assets	(8,581.7)	(8,777.9)
Accounts payable	0.0	0.0
Accrued liabilities	0.0	0.0
Intercompany notes payable	(2,601.5)	(2,390.8)
Short-term debt and current portion of long-term debt	0.0	0.0
Total Current Liabilities	(2,601.5)	(2,390.8)
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	(2,801.5)	(2,590.8)
Redeemable noncontrolling interest	0.0	0.0
Total Stockholders’ Equity	(5,780.2)	(6,187.1)
Total Liabilities and Stockholders’ Equity	$ (8,581.7)	$ (8,777.9)