Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Millions	Total	Common Stock	Capital in Excess of Par Value	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Loss
Beginning Balance at Dec. 31, 2016	$ 394.1	$ 65.4	$ 200.3	$ 301.8	$ (81.4)	$ (92.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	18.7			18.7
Total other comprehensive income	6.5					6.5	[1]
Cash dividends declared	(8.4)			(8.4)
Stock-based payments:
Stock-based compensation	2.1		2.1
Stock option exercises and other	1.3	0.3	2.2		(1.2)
Performance share unit transactions	(1.9)	0.2	(0.2)		(1.9)
Ending Balance at Jun. 30, 2017	412.4	65.9	204.4	312.1	(84.5)	(85.5)
Beginning Balance at Dec. 31, 2017	457.4	66.1	207.7	346.6	(86.1)	(76.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	39.8			39.8
Total other comprehensive income	(0.4)					(0.4)	[1]
Cash dividends declared	(9.0)			(9.0)
Stock-based payments:
Stock-based compensation	3.3		3.3
Stock option exercises and other	1.3	0.2	1.7		(0.6)
Ending Balance at Jun. 30, 2018	$ 492.4	$ 66.3	$ 212.7	$ 377.4	$ (86.7)	$ (77.3)

[1] Amounts in parentheses indicate losses.