Statements of Consolidated Income - USD ($) shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Statement [Abstract]
Net sales	$ 334.9	$ 367.2	$ 678.1	$ 738.9
Cost of products sold:
Cost of products sold, excluding depreciation and amortization and other items	250.4	294.8	512.4	597.1
Lower of cost or market inventory write-down	0.0	0.0	4.9	0.0
Unrealized (gain) loss on derivative instruments	(10.9)	1.5	(14.9)	6.0
Depreciation and amortization	9.0	8.1	17.7	16.1
Selling, general, administrative, research and development	27.5	23.6	53.6	46.3
Net periodic postretirement benefit cost relating to Salaried VEBA	0.9	0.6	1.7	1.2
Loss (gain) on removal of Union VEBA net assets	0.0	1.6	(0.1)	493.8
Total selling, general, administrative, research and development	28.4	25.8	55.2	541.3
Other operating charges, net	0.1	0.0	0.1	0.0
Total costs and expenses	277.0	330.2	575.4	1,160.5
Operating income (loss)	57.9	37.0	102.7	(421.6)
Other (expense) income:
Interest expense	(5.5)	(5.2)	(9.2)	(15.0)
Other (expense) income, net	(10.7)	0.4	(10.4)	0.8
Income (loss) before income taxes	41.7	32.2	83.1	(435.8)
Income tax (provision) benefit	(15.7)	(12.0)	(30.8)	163.8
Net income (loss)	$ 26.0	$ 20.2	$ 52.3	$ (272.0)
Net income (loss) per common share:
Basic (in dollars per share)	$ 1.45	$ 1.19	$ 2.92	$ (15.78)
Diluted (in dollars per share)	$ 1.43	$ 1.11	$ 2.87	$ (15.78)
Weighted-average number of common shares outstanding (in thousands):
Basic (shares)	17,871	17,006	17,867	17,233
Diluted (shares)	18,194	18,192	18,194	17,233
Cash dividends declared (in dollars per share)	$ 0.45	$ 0.40	$ 0.90	$ 0.80