Consolidated Statements of Changes in Stockholders' Equity (USD $) In Millions, except Share data	Total	Common Stock	Treasury Stock	Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning Balance at Dec. 31, 2011	$ 971.3	$ 1.0	$ 0	$ 351.8	$ 716.3	$ (97.8)
Beginning Balance (in shares) at Dec. 31, 2011		98,325,000	(2,000)
Common stock repurchases and retirements (in shares)	(1,507,659)	(1,510,000)	2,000
Common stock repurchases and retirements	(45.2)	0	0	(9.3)	(35.9)	0
Common stock dividends declared	(98.1)	0	0	0	(98.1)	0
Restricted stock grants and cancellations (in shares)		383,000	0
Restricted stock grants and cancellations	1.6	0	0	1.6	0	0
Exercise of stock options (in shares)		945,000	0
Exercise of stock options	22.3	0	0	22.3	0	0
Share-based compensation expense	11.7	0	0	11.7	0	0
Other	0.7	0	0	0.7	0	0
Comprehensive income	144.0	0	0	0	160.2	(16.2)
Ending Balance at Dec. 31, 2012	1,008.3	1.0	0	378.8	742.5	(114.0)
Ending Balance (in shares) at Dec. 31, 2012		98,143,000	0
Common stock repurchases and retirements (in shares)	(171,263)	(171,000)	0
Common stock repurchases and retirements	(7.8)	0	0	(1.1)	(6.7)	0
Common stock withheld and retired to cover taxes on vested stock awards (in shares)		(224,000)	0
Common stock withheld and retired to cover taxes on vested stock awards	(11.0)	0	0	(1.4)	(9.6)	0
Common stock dividends declared	(148.4)	0	0	0	(148.4)	0
Restricted stock grants and cancellations (in shares)		297,000	0
Restricted stock grants and cancellations	6.9	0	0	6.9	0	0
Exercise of stock options (in shares)		127,000	0
Exercise of stock options	3.7	0	0	3.7	0	0
Share-based compensation expense	14.8	0	0	14.8	0	0
Other	0	0	0	0	0	0
Comprehensive income	490.3	0	0	0	441.3	49.0
Ending Balance at Dec. 31, 2013	1,356.8	1.0	0	401.7	1,019.1	(65.0)
Ending Balance (in shares) at Dec. 31, 2013		98,172,000	0
Common stock withheld and retired to cover taxes on vested stock awards (in shares)		(183,000)	0
Common stock withheld and retired to cover taxes on vested stock awards	(13.2)	0	0	(1.2)	(12.0)	0
Common stock dividends declared	(157.5)	0	0	0	(157.5)	0
Restricted stock grants and cancellations (in shares)		228,000	0
Restricted stock grants and cancellations	9.7	0	0	9.7	0	0
Exercise of stock options (in shares)		151,000	0
Exercise of stock options	6.3	0	0	6.3	0	0
Share-based compensation expense	15.6	0	0	15.6	0	0
Comprehensive income	303.7	0	0	0	392.6	(88.9)
Ending Balance at Dec. 31, 2014	$ 1,521.4	$ 1.0	$ 0	$ 432.1	$ 1,242.2	$ (153.9)
Ending Balance (in shares) at Dec. 31, 2014		98,368,000	0