Present and Prospective Accounting Pronouncements Effect of change related to ASU 2014-09 (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales	$ (810.8)	$ (694.1)	$ (1,502.1)	$ (1,305.0)
Cost of sales	(550.2)	(511.8)	(1,064.7)	(994.6)
Selling, general and administrative expense	(50.1)	(47.2)	(100.7)	(95.9)
Provision for income taxes	51.2	36.0	80.9	51.5
Net income	162.7	$ 94.5	253.6	$ 149.5
Receivables, net of allowance of doubtful accounts	(162.3)		(162.3)			$ (142.5)
Inventories	(286.4)		(286.4)			(259.1)
Income taxes payable	15.7		15.7			4.5
Retained earnings	(1,508.4)		(1,508.4)			$ (1,280.1)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales	(7.6)		(18.7)
Cost of sales	(3.8)		(10.3)
Selling, general and administrative expense	(1.1)		(1.9)
Provision for income taxes	(0.7)		(1.6)
Net income	(2.0)		(4.9)
Receivables, net of allowance of doubtful accounts	(38.5)		(38.5)
Inventories	(26.1)		(26.1)
Income taxes payable	3.1		3.1
Retained earnings	(9.3)		(9.3)
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales	(818.4)		(1,520.8)
Cost of sales	(554.0)		(1,075.0)
Selling, general and administrative expense	(51.2)		(102.6)
Provision for income taxes	51.9		82.5
Net income	164.7		258.5
Receivables, net of allowance of doubtful accounts	(200.8)		(200.8)
Inventories	(260.3)		(260.3)
Income taxes payable	18.8		18.8
Retained earnings	$ (1,517.7)		$ (1,517.7)
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