Present and Prospective Accounting Pronouncements Effect of change related to ASU 2014-09 (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales	$ 691.3	$ 610.9
Cost of sales	514.5	482.8
Selling, general and administrative expense	50.6	48.7
Provision for income taxes	29.7	15.5
Net income	90.9	$ 55.0
Receivables, net of allowance of doubtful accounts	149.3		$ 142.5
Inventories	329.4		259.1
Income taxes payable	21.6		4.5
Retained earnings	1,364.4		$ 1,280.1
Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Receivables, net of allowance of doubtful accounts	(21.7)
Inventories	15.8
Retained earnings	(4.4)
Accounting Standards Update 2014-09 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales	702.4
Cost of sales	521.0
Selling, general and administrative expense	51.4
Provision for income taxes	30.6
Net income	93.8
Receivables, net of allowance of doubtful accounts	181.3
Inventories	307.1
Income taxes payable	22.5
Retained earnings	1,367.3
Accounting Standards Update 2014-09 [Member] | Calculated under Revenue Guidance in Effect before Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales	(11.1)
Cost of sales	(6.5)
Selling, general and administrative expense	(0.8)
Provision for income taxes	(0.9)
Net income	(2.9)
Receivables, net of allowance of doubtful accounts	(32.0)
Inventories	22.3
Income taxes payable	(0.9)
Retained earnings	$ (2.9)