Present and Prospective Accounting Pronouncements Effect of change related to 2017-07 and other reclassifications (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales	$ 2,084.0	$ 1,998.1	$ 1,829.1
Selling, general and administrative expense	(209.3)	(191.3)	(185.1)
Other operating credits and charges, net	(2.2)	4.9	17.4
Income from operations	526.1	532.8	210.2
Total non-operating income (expense)	$ (2.1)	(22.6)	(45.3)
Scenario, Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales (exclusive of depreciation and amortization shown separately below)		1,882.0	1,724.0
Depreciation and amortization		123.3	112.8
Selling, general and administrative expense		(190.4)	(183.6)
Other operating credits and charges, net		(8.0)
Income from operations		523.4	204.0
Total non-operating income (expense)		(13.2)	(39.1)
Reclassifications other than adoptions [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Depreciation and amortization		0.0	0.0
Reclassifications other than adoptions [Member] | Scenario, Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales		120.1	109.6
Depreciation and amortization		(123.3)	(112.8)
Selling, general and administrative expense		(3.2)	(3.2)
Other operating credits and charges, net		0.0
Income from operations		0.0	0.0
Total non-operating income (expense)		0.0	0.0
Accounting Standards Update 2017-07 [Member] | Scenario, Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales		(4.0)	(4.5)
Depreciation and amortization		0.0
Selling, general and administrative expense		2.3	1.7
Other operating credits and charges, net		3.1
Income from operations		9.4	6.2
Total non-operating income (expense)		$ (9.4)	$ (6.2)