Consolidated Statement of Stockholders' Equity (USD $) In Millions, unless otherwise specified	Total	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]
Stockholders' Equity Attributable to Parent - Period Start at Dec. 31, 2011	$ 460.5	$ 409.4	$ (181.8)	$ (4.0)	$ 236.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	3.0	3.0
Adjustments to Additional Paid in Capital, Other	(0.3)	(0.3)
Net Income	51.3				51.3
Treasury stock repurchases	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Net of Tax	(1.4)			(1.4)
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax	(0.4)			0.4
Stockholders' Equity Attributable to Parent - Period End at Dec. 31, 2012	513.5	412.1	(181.8)	(5.0)	288.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	4.0	4.0
Adjustments to Additional Paid in Capital, Other	4.1	4.1
Net Income	26.7				26.7
Treasury stock repurchases	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Net of Tax	2.1			2.1
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax	(0.3)			0.3
Stockholders' Equity Attributable to Parent - Period End at Dec. 31, 2013	550.7	420.2	(181.8)	(2.6)	314.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	4.6	4.6
Adjustments to Additional Paid in Capital, Other	2.6	2.6
Net Income	64.3				64.3
Treasury stock repurchases	(2.1)		(2.1)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Net of Tax	0.1			0.1
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax	(0.3)			(0.3)
Stockholders' Equity Attributable to Parent - Period End at Dec. 31, 2014	$ 620.5	$ 427.4	$ (183.9)	$ (2.2)	$ 379.2