Present and Prospective Accounting Pronouncements Effect of change related to ASU 2017-07 and other reclassifications (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales	$ 514.5	$ 482.8
Depreciation and amortization	31.0	30.6
Selling, general and administrative expense	50.6	48.7
Income from operations	127.2	75.4
Total non-operating income (expense)	$ (2.6)	(4.9)
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)		453.9
Depreciation and amortization		30.6
Selling, general and administrative expense		48.6
Income from operations		73.8
Total non-operating income (expense)		(3.3)
Reclassifications other than adoptions [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Depreciation and amortization		0.0
Reclassifications other than adoptions [Member] | Scenario, Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales		29.9
Depreciation and amortization		(30.6)
Selling, general and administrative expense		0.7
Income from operations		0.0
Total non-operating income (expense)		0.0
Accounting Standards Update 2017-07 [Member] | Scenario, Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales		(1.0)
Depreciation and amortization		0.0
Selling, general and administrative expense		(0.6)
Income from operations		1.6
Total non-operating income (expense)		$ (1.6)