Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Foreign Currency Translation [Abstract]
Balance at beginning of period		$ (1.7)	$ (1.0)	$ (2.1)	$ 1.0
Foreign currency translation gain (loss)		0.1	0.0	0.5	(2.0)
Balance at end of period		(1.6)	(1.0)	(1.6)	(1.0)
Cash flow hedges
Balance at beginning of period		21.4	(24.5)	(34.0)	(32.2)
Other comprehensive income (loss):
Gains (losses) arising in period		2.4	(27.5)	35.3	(47.0)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax		(2.9)	0.0	0.0	0.0
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax		5.3	(27.5)	35.3	(47.0)
Reclassification of losses (gains) to net income (loss)		(1.4)	14.2	26.3	41.4
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax		(2.3)	0.0	0.0	0.0
Net amount of reclassification of losses (gains) to net income (loss)		0.9	14.2	26.3	41.4
Total other comprehensive income (loss), net of tax		6.2	(13.3)	61.6	(5.6)
Balance at end of period		27.6	(37.8)	27.6	(37.8)
Unrealized holding gains on securities
Balance at beginning of period		0.0	0.4	0.0	0.4
Balance at end of period		0.0	0.4	0.0	0.4
Pension and OPEB plans
Balance at beginning of period		(165.5)	(187.3)	(151.1)	(173.6)
Other comprehensive income (loss):
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost (Credit) Arising During Period, before Tax		8.9	0.0	8.9	0.0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax		(12.8)	0.0	(12.8)	0.0
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, before Reclassification Adjustments and Tax		21.7	0.0	21.7	0.0
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, before Reclassification Adjustments, Tax		0.0	0.0	0.0	0.0
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, before Reclassification Adjustments, Net of Tax		21.7	0.0	21.7	0.0
Reclassification to net income (loss):
Other Comprehensive (Income) Loss, Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), before Tax		(13.5)	(15.1)	(41.1)	(45.2)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax		11.8	8.2	23.7	24.6
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax		(1.7)	(6.9)	(17.4)	(20.6)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Tax		1.3	0.0	0.0	0.0
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Net of Tax		(3.0)	(6.9)	(17.4)	(20.6)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax		(24.7)	(6.9)	(39.1)	(20.6)
Balance at end of period		(190.2)	(194.2)	(190.2)	(194.2)
Cost of Sales [Member]
Other comprehensive income (loss):
Reclassification of losses (gains) to net income (loss)	[1]	(1.4)	14.2	26.3	41.4
Pension and OPEB Expense (Income) [Member]
Reclassification to net income (loss):
Other Comprehensive (Income) Loss, Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), before Tax	[2]	(13.5)	(15.1)	(41.1)	(45.2)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax	[2]	$ 11.8	$ 8.2	$ 23.7	$ 24.6

[1] Included in cost of products sold.

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