Consolidated Statements of Stockholders' Equity (USD $) In Millions, unless otherwise specified	Total	Common Stock Par	Common Stock Additional Paid-In Capital	Accumulated Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Balance at Dec. 31, 2011	$ 802.2	$ 1.0	$ 589.2	$ 283.9	$ (39.8)	$ (32.1)
Increase (Decrease) in Stockholders' Equity
Net income	164.3			164.3
Change in other comprehensive income (loss) - net of tax	7.9				7.9
Stock based compensation	27.8		27.8
Acquisition of treasury stock	(8.1)					(8.1)
Balance at Dec. 31, 2012	994.1	1.0	617.0	448.2	(31.9)	(40.2)
Increase (Decrease) in Stockholders' Equity
Net income	187.9			187.9
Change in other comprehensive income (loss) - net of tax	42.6				42.6
Stock based compensation	25.3		25.3
Acquisition of treasury stock	(89.5)					(89.5)
Balance at Dec. 31, 2013	1,160.4	1.0	642.3	636.1	10.7	(129.7)
Increase (Decrease) in Stockholders' Equity
Net income	209.4			209.4
Change in other comprehensive income (loss) - net of tax	(80.4)				(80.4)
Stock based compensation	36.2		36.2
Acquisition of treasury stock	(175.7)					(175.7)
Balance at Dec. 31, 2014	$ 1,149.9	$ 1.0	$ 678.5	$ 845.5	$ (69.7)	$ (305.4)