Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Foreign currency translation
Balance at beginning of period		$ 2.2	$ (3.3)	$ 1.1	$ (3.6)
Other comprehensive income (loss)—foreign currency translation gain (loss)		(2.2)	2.3	(1.1)	2.6
Balance at end of period		0.0	(1.0)	0.0	(1.0)
Cash flow hedges
Balance at beginning of period		14.1	31.3	22.3	39.9
Cumulative effect of adopting new hedging standard							$ 0.0
Other comprehensive income (loss):
Gains (losses) arising in period		(4.1)	(8.2)	(5.5)	(16.2)
Income tax expense (benefit) (b)	[1]	0.0	0.0	0.0	0.0
Gains (losses) arising in period, net of tax		(4.1)	(8.2)	(5.5)	(16.2)
Reclassification of losses (gains) to net income:
Recorded in cost of products sold		(5.5)	(1.3)	(13.1)	(1.9)
Income tax (expense) benefit (b)	[1]	0.0	0.0	0.0	0.0
Net amount of reclassification of losses (gains) to net income, net of tax		(5.5)	(1.3)	(13.1)	(1.9)
Total other comprehensive income (loss), net of tax		(9.6)	(9.5)	(18.6)	(18.1)
Balance at end of period		4.5	21.8	4.5	21.8
Pension and OPEB plans
Balance at beginning of period		(72.4)	(136.8)	(73.6)	(125.0)
Reclassification to net income:
Prior service costs (credits) (a)		(2.5)	(13.6)	(4.9)	(27.0)
Actuarial (gains) losses (a)		3.6	1.7	7.2	3.3
Subtotal		1.1	(11.9)	2.3	(23.7)
Income tax (expense) benefit (b)	[1]	0.0	0.0	0.0	0.0
Amount of reclassification to net income, net of tax		1.1	(11.9)	2.3	(23.7)
Total other comprehensive income (loss), net of tax		1.1	(11.9)	2.3	(23.7)
Balance at end of period		(71.3)	(148.7)	(71.3)	(148.7)
Cost of Sales [Member]
Reclassification of losses (gains) to net income:
Recorded in cost of products sold		(5.5)	(1.3)	(13.1)	(1.9)
Pension and OPEB Expense (Income) [Member]
Reclassification to net income:
Prior service costs (credits) (a)	[2]	(2.5)	(13.6)	(4.9)	(27.0)
Actuarial (gains) losses (a)	[2]	$ 3.6	$ 1.7	$ 7.2	$ 3.3
Accumulated Other Comprehensive Income (Loss) [Member]
Cash flow hedges
Cumulative effect of adopting new hedging standard						$ 0.0	$ 0.8	$ 0.0	$ 0.0

[1] Included in income tax expense (benefit)

[2] Included in pension and OPEB (income) expense