Condensed Guarantor and Non-Guarantor Financial Information, Balance Sheets (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Current assets:
Cash and cash equivalents	$ 34.4	$ 55.2	$ 70.7
Short-term investments	195.5	231.0
Receivables:
Trade receivables – net	157.0	137.7
Intercompany receivables	0.0	0.0
Other	11.8	11.9
Inventories	203.5	201.6
Prepaid expenses and other current assets	34.0	18.5
Total current assets	636.2	655.9
Investments in and advances to subsidiaries	0.0	0.0
Property, plant and equipment – net	535.8	530.9
Long-term intercompany loans receivable	0.0	0.0
Deferred tax assets – net	140.8	159.7
Intangible assets – net	26.0	26.4
Goodwill	37.2	37.2
Other assets	37.1	33.4
Total	1,413.1	1,443.5
Current liabilities:
Accounts payable	84.4	75.8
Intercompany loans payable	0.0	0.0
Accrued salaries, wages and related expenses	29.1	49.1
Other accrued liabilities	40.4	40.1
Total current liabilities	153.9	165.0
Net liabilities of Salaried VEBA	28.3	28.6
Deferred tax liabilities	3.3	3.3
Long-term intercompany loans payable	0.0	0.0
Long-term liabilities	60.1	73.2
Long-term debt	368.9	368.7
Total liabilities	614.5	638.8
Total stockholders' equity	798.6	804.7
Total	1,413.1	1,443.5
Consolidating Adjustments
Current assets:
Cash and cash equivalents	0.0	0.0
Short-term investments	0.0	0.0
Receivables:
Trade receivables – net	0.0	0.0
Intercompany receivables	(86.5)	(86.5)
Other	0.0	0.0
Inventories	(4.2)	(3.9)
Prepaid expenses and other current assets	0.0	(0.5)
Total current assets	(90.7)	(90.9)
Investments in and advances to subsidiaries	(1,099.6)	(1,052.5)
Property, plant and equipment – net	0.0	0.0
Long-term intercompany loans receivable	(37.8)	(85.1)
Deferred tax assets – net	4.8	4.8
Intangible assets – net	0.0	0.0
Goodwill	0.0	0.0
Other assets	0.0	0.0
Total	(1,223.3)	(1,223.7)
Current liabilities:
Accounts payable	0.0	0.0
Intercompany loans payable	(86.5)	(86.5)
Accrued salaries, wages and related expenses	0.0	0.0
Other accrued liabilities	(2.5)	(14.7)
Total current liabilities	(89.0)	(101.2)
Net liabilities of Salaried VEBA	0.0	0.0
Deferred tax liabilities	0.0	0.0
Long-term intercompany loans payable	(37.8)	(85.1)
Long-term liabilities	0.0	0.0
Long-term debt	0.0	0.0
Total liabilities	(126.8)	(186.3)
Total stockholders' equity	(1,096.5)	(1,037.4)
Total	(1,223.3)	(1,223.7)
Parent
Current assets:
Cash and cash equivalents	0.0	0.0
Short-term investments	0.0	0.0
Receivables:
Trade receivables – net	0.0	0.0
Intercompany receivables	85.8	85.8
Other	0.0	0.0
Inventories	0.0	0.0
Prepaid expenses and other current assets	0.1	0.1
Total current assets	85.9	85.9
Investments in and advances to subsidiaries	1,059.1	1,012.4
Property, plant and equipment – net	0.0	0.0
Long-term intercompany loans receivable	33.6	80.2
Deferred tax assets – net	0.0	0.0
Intangible assets – net	0.0	0.0
Goodwill	0.0	0.0
Other assets	0.0	0.0
Total	1,178.6	1,178.5
Current liabilities:
Accounts payable	2.7	2.2
Intercompany loans payable	0.0	0.0
Accrued salaries, wages and related expenses	0.0	0.0
Other accrued liabilities	8.4	2.9
Total current liabilities	11.1	5.1
Net liabilities of Salaried VEBA	0.0	0.0
Deferred tax liabilities	0.0	0.0
Long-term intercompany loans payable	0.0	0.0
Long-term liabilities	0.0	0.0
Long-term debt	368.9	368.7
Total liabilities	380.0	373.8
Total stockholders' equity	798.6	804.7
Total	1,178.6	1,178.5
Guarantor Subsidiaries
Current assets:
Cash and cash equivalents	29.7	52.9
Short-term investments	195.5	231.0
Receivables:
Trade receivables – net	151.5	133.1
Intercompany receivables	0.1	0.1
Other	10.9	11.4
Inventories	199.7	197.5
Prepaid expenses and other current assets	33.5	18.0
Total current assets	620.9	644.0
Investments in and advances to subsidiaries	40.5	40.1
Property, plant and equipment – net	504.9	499.5
Long-term intercompany loans receivable	0.0	0.0
Deferred tax assets – net	136.0	154.9
Intangible assets – net	26.0	26.4
Goodwill	37.2	37.2
Other assets	37.1	33.4
Total	1,402.6	1,435.5
Current liabilities:
Accounts payable	76.1	68.9
Intercompany loans payable	86.4	86.4
Accrued salaries, wages and related expenses	27.8	47.2
Other accrued liabilities	34.4	52.6
Total current liabilities	224.7	255.1
Net liabilities of Salaried VEBA	28.3	28.6
Deferred tax liabilities	0.0	0.0
Long-term intercompany loans payable	37.8	85.1
Long-term liabilities	57.4	70.5
Long-term debt	0.0	0.0
Total liabilities	348.2	439.3
Total stockholders' equity	1,054.4	996.2
Total	1,402.6	1,435.5
Non-Guarantor Subsidiaries
Current assets:
Cash and cash equivalents	4.7	2.3
Short-term investments	0.0	0.0
Receivables:
Trade receivables – net	5.5	4.6
Intercompany receivables	0.6	0.6
Other	0.9	0.5
Inventories	8.0	8.0
Prepaid expenses and other current assets	0.4	0.9
Total current assets	20.1	16.9
Investments in and advances to subsidiaries	0.0	0.0
Property, plant and equipment – net	30.9	31.4
Long-term intercompany loans receivable	4.2	4.9
Deferred tax assets – net	0.0	0.0
Intangible assets – net	0.0	0.0
Goodwill	0.0	0.0
Other assets	0.0	0.0
Total	55.2	53.2
Current liabilities:
Accounts payable	5.6	4.7
Intercompany loans payable	0.1	0.1
Accrued salaries, wages and related expenses	1.3	1.9
Other accrued liabilities	0.1	(0.7)
Total current liabilities	7.1	6.0
Net liabilities of Salaried VEBA	0.0	0.0
Deferred tax liabilities	3.3	3.3
Long-term intercompany loans payable	0.0	0.0
Long-term liabilities	2.7	2.7
Long-term debt	0.0	0.0
Total liabilities	13.1	12.0
Total stockholders' equity	42.1	41.2
Total	$ 55.2	$ 53.2