Revenue Recognition (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended		6 Months Ended
		Jan. 01, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Effect of LIFO Inventory Liquidation on Income		$ 5.0
Contract assets		55.6	$ 52.6		$ 52.6		$ 0.0
Inventories		167.2	177.2		177.2		207.9
Total current assets		671.5	704.8		704.8		656.6
Deferred tax assets, net		68.7	51.5		51.5		72.0
Assets		1,396.8	1,423.8		1,423.8		1,385.2
Other accrued liabilities		42.0	29.9		29.9		40.5
Total current liabilities		174.6	194.1		194.1		173.1
Total liabilities		640.4	662.8		662.8		638.9
Retained earnings		95.6	123.1		123.1		85.5
Total stockholders' equity		756.4	761.0		761.0		746.3
Total liabilities and stockholders’ equity		1,396.8	1,423.8		1,423.8		1,385.2
Net sales			415.4	$ 356.3	803.4	$ 711.6
Cost of products sold, excluding depreciation and amortization and other items	[1]		343.4	289.6	660.1	552.3
Operating income			34.7	12.5	71.8	71.8
Income before income taxes			28.5	6.9	60.1	61.4
Income tax provision			(7.8)	(2.2)	(13.7)	(20.7)
Net income			$ 20.7	$ 4.7	$ 46.4	$ 40.7
Basic earnings per share (in dollars per share)			$ 1.24	$ 0.28	$ 2.78	$ 2.37
Diluted earnings per share (in dollars per share)			$ 1.22	$ 0.27	$ 2.74	$ 2.34
Comprehensive income			$ 27.1	$ 5.8	$ 44.5	$ 43.1
Contract assets					3.0	0.0
Inventories					(10.0)	1.7
Accrued liabilities					(10.8)	(9.8)
Net cash provided by (used in) operating activities	[2]				84.0	$ 73.1
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Contract assets		55.6	(52.6)		(52.6)
Inventories		(40.7)	32.7		32.7
Total current assets		14.9	(19.9)		(19.9)
Deferred tax assets, net		(3.3)	3.3		3.3
Assets		11.6	(16.6)		(16.6)
Other accrued liabilities		1.5	(3.1)		(3.1)
Total current liabilities		1.5	(3.1)		(3.1)
Total liabilities		1.5	(3.1)		(3.1)
Retained earnings		10.1	(13.5)		(13.5)
Total stockholders' equity		10.1	(13.5)		(13.5)
Total liabilities and stockholders’ equity		$ 11.6	(16.6)		(16.6)
Net sales			4.9		3.2
Cost of products sold, excluding depreciation and amortization and other items			3.4		7.6
Operating income			1.5		(4.4)
Income before income taxes			1.5		(4.4)
Income tax provision			(0.4)		1.0
Net income			$ 1.1		$ (3.4)
Basic earnings per share (in dollars per share)			$ 0.07		$ (0.20)
Diluted earnings per share (in dollars per share)			$ 0.06		$ (0.20)
Comprehensive income			$ 1.1		$ (3.4)
Contract assets					(3.0)
Inventories					8.0
Accrued liabilities					(1.6)
Net cash provided by (used in) operating activities					0.0
Calculated under Revenue Guidance in Effect before Topic 606
Contract assets			0.0		0.0		0.0
Inventories			209.9		209.9		207.9
Total current assets			684.9		684.9		656.6
Deferred tax assets, net			54.8		54.8		72.0
Assets			1,407.2		1,407.2		1,385.2
Other accrued liabilities			26.8		26.8		40.5
Total current liabilities			191.0		191.0		173.1
Total liabilities			659.7		659.7		638.9
Retained earnings			109.6		109.6		85.5
Total stockholders' equity			747.5		747.5		746.3
Total liabilities and stockholders’ equity			1,407.2		1,407.2		$ 1,385.2
Net sales			420.3		806.6
Cost of products sold, excluding depreciation and amortization and other items			346.8		667.7
Operating income			36.2		67.4
Income before income taxes			30.0		55.7
Income tax provision			(8.2)		(12.7)
Net income			$ 21.8		$ 43.0
Basic earnings per share (in dollars per share)			$ 1.31		$ 2.58
Diluted earnings per share (in dollars per share)			$ 1.28		$ 2.54
Comprehensive income			$ 28.2		$ 41.1
Contract assets					0.0
Inventories					(2.0)
Accrued liabilities					(12.4)
Net cash provided by (used in) operating activities					$ 84.0

[1] See Note 4 for discussion of our adoption of ASU 2017-12 (as defined in Note 1) and the related reclassification of amounts previously presented in the Statements of Consolidated Income within Unrealized loss (gain) on derivative instruments and now included within Cost of products sold, excluding depreciation and amortization and other items.

[2] See Note 8 for adjustments made to arrive at our Consolidated Balance Sheet as of January 1, 2018 upon adopting ASC 606 (as defined in Note 1).