Condensed Guarantor and Non-Guarantor Financial Statements, Comprehensive Income Statements (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
CONDENSED CONSOLIDATING STATEMENT OF COMPREHENSIVE INCOME
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 (loss) income	57.9	37.0	102.7	(421.6)
Other (expense) income:
Interest expense	(5.5)	(5.2)	(9.2)	(15.0)
Other income, net	(10.7)	0.4	(10.4)	0.8
(Loss) income before income taxes	41.7	32.2	83.1	(435.8)
Income tax (provision) benefit	(15.7)	(12.0)	(30.8)	163.8
Earnings in equity of subsidiaries	0.0	0.0	0.0	0.0
Net income	26.0	20.2	52.3	(272.0)
Comprehensive income	26.9	20.6	54.1	(204.7)
Consolidating Adjustments
CONDENSED CONSOLIDATING STATEMENT OF COMPREHENSIVE INCOME
Net sales	(20.0)	(24.6)	(38.9)	(51.0)
Cost of products sold:
Cost of products sold, excluding depreciation and amortization and other items	(19.1)	(23.5)	(37.3)	(49.2)
Lower of cost or market inventory write-down			0.0
Unrealized (gain) loss on derivative instruments	0.0	0.0	0.0	0.0
Depreciation and amortization	0.0	0.0	0.0	0.0
Selling, general, administrative, research and development	(0.9)	(0.5)	(1.4)	(1.1)
Net periodic postretirement benefit cost relating to Salaried VEBA	0.0	0.0	0.0	0.0
Loss (gain) on removal of Union VEBA net assets		0.0	0.0	0.0
Total selling, general, administrative, research and development	(0.9)	(0.5)	(1.4)	(1.1)
Other operating charges, net	0.0		0.0
Total costs and expenses	(20.0)	(24.0)	(38.7)	(50.3)
Operating (loss) income	0.0	(0.6)	(0.2)	(0.7)
Other (expense) income:
Interest expense	0.0	0.0	0.0	0.2
Other income, net	0.0	0.0	0.0	(0.2)
(Loss) income before income taxes	0.0	(0.6)	(0.2)	(0.7)
Income tax (provision) benefit	7.1	2.4	9.1	6.3
Earnings in equity of subsidiaries	(44.8)	(28.6)	(76.5)	252.0
Net income	(37.7)	(26.8)	(67.6)	257.6
Comprehensive income	(38.6)	(27.2)	(69.4)	190.3
Parent
CONDENSED CONSOLIDATING STATEMENT OF COMPREHENSIVE INCOME
Net sales	0.0	0.0	0.0	0.0
Cost of products sold:
Cost of products sold, excluding depreciation and amortization and other items	0.0	0.0	0.0	0.0
Lower of cost or market inventory write-down			0.0
Unrealized (gain) loss on derivative instruments	0.0	0.0	0.0	0.0
Depreciation and amortization	0.0	0.0	0.0	0.0
Selling, general, administrative, research and development	1.6	1.4	2.4	2.4
Net periodic postretirement benefit cost relating to Salaried VEBA	0.0	0.0	0.0	0.0
Loss (gain) on removal of Union VEBA net assets		0.0	0.0	0.0
Total selling, general, administrative, research and development	1.6	1.4	2.4	2.4
Other operating charges, net	0.0		0.0
Total costs and expenses	1.6	1.4	2.4	2.4
Operating (loss) income	(1.6)	(1.4)	(2.4)	(2.4)
Other (expense) income:
Interest expense	(5.9)	(4.9)	(10.2)	(14.4)
Other income, net	(11.0)	0.0	(11.0)	0.0
(Loss) income before income taxes	(18.5)	(6.3)	(23.6)	(16.8)
Income tax (provision) benefit	0.0	0.0	0.0	0.0
Earnings in equity of subsidiaries	44.5	26.5	75.9	(255.2)
Net income	26.0	20.2	52.3	(272.0)
Comprehensive income	26.9	20.6	54.1	(204.7)
Guarantor Subsidiaries
CONDENSED CONSOLIDATING STATEMENT OF COMPREHENSIVE INCOME
Net sales	327.3	358.3	663.0	721.7
Cost of products sold:
Cost of products sold, excluding depreciation and amortization and other items	246.0	289.4	503.1	585.8
Lower of cost or market inventory write-down			4.9
Unrealized (gain) loss on derivative instruments	(10.9)	1.5	(14.9)	6.0
Depreciation and amortization	8.5	7.8	16.7	15.5
Selling, general, administrative, research and development	23.8	19.5	47.4	40.2
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		1.6	(0.1)	493.8
Total selling, general, administrative, research and development	24.7	21.7	49.0	535.2
Other operating charges, net	0.1		0.1
Total costs and expenses	268.4	320.4	558.9	1,142.5
Operating (loss) income	58.9	37.9	104.1	(420.8)
Other (expense) income:
Interest expense	0.4	(0.3)	1.0	(0.8)
Other income, net	0.2	0.3	0.5	0.8
(Loss) income before income taxes	59.5	37.9	105.6	(420.8)
Income tax (provision) benefit	(22.6)	(15.8)	(39.5)	156.1
Earnings in equity of subsidiaries	0.3	2.1	0.6	3.2
Net income	37.2	24.2	66.7	(261.5)
Comprehensive income	38.1	24.6	68.4	(194.3)
Non-Guarantor Subsidiaries
CONDENSED CONSOLIDATING STATEMENT OF COMPREHENSIVE INCOME
Net sales	27.6	33.5	54.0	68.2
Cost of products sold:
Cost of products sold, excluding depreciation and amortization and other items	23.5	28.9	46.6	60.5
Lower of cost or market inventory write-down			0.0
Unrealized (gain) loss on derivative instruments	0.0	0.0	0.0	0.0
Depreciation and amortization	0.5	0.3	1.0	0.6
Selling, general, administrative, research and development	3.0	3.2	5.2	4.8
Net periodic postretirement benefit cost relating to Salaried VEBA	0.0	0.0	0.0	0.0
Loss (gain) on removal of Union VEBA net assets		0.0	0.0	0.0
Total selling, general, administrative, research and development	3.0	3.2	5.2	4.8
Other operating charges, net	0.0		0.0
Total costs and expenses	27.0	32.4	52.8	65.9
Operating (loss) income	0.6	1.1	1.2	2.3
Other (expense) income:
Interest expense	0.0	0.0	0.0	0.0
Other income, net	0.1	0.1	0.1	0.2
(Loss) income before income taxes	0.7	1.2	1.3	2.5
Income tax (provision) benefit	(0.2)	1.4	(0.4)	1.4
Earnings in equity of subsidiaries	0.0	0.0	0.0	0.0
Net income	0.5	2.6	0.9	3.9
Comprehensive income	$ 0.5	$ 2.6	$ 1.0	$ 4.0