Stock Incentive Plans (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2010 years	Dec. 31, 2009 years	Dec. 31, 2008 years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for grant	12,500,000
Shares available for future issuance	2,200,000
Status of Stock Options
Proceeds from stock based compensation - net	$ 53.0	$ 67.1	$ 8.7
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option compensation expense			6.6
Stock option compensation expense, net of tax			5.1
Stock option compensation expense, net of tax - Basic			$ 0.04
Stock option compensation expense, net of tax - Diluted			$ 0.04
Status of Stock Options
Shares outstanding under option, beginning balance	3,253,000	5,177,000	5,798,000
Shares outstanding under option, exercised	(1,033,000)	(1,888,000)	(381,000)
Shares outstanding under option, forfeited		(36,000)	(240,000)
Shares outstanding under option, ending balance	2,220,000	3,253,000	5,177,000
Weighted average exercise price, beginning balance	$ 28.64	$ 27.98	$ 27.86
Weighted average exercise price, exercised	$ 27.15	$ 26.73	$ 23.89
Weighted average exercise price, forfeited		$ 33.95	$ 32.16
Weighted average exercise price, ending balance		$ 28.64	$ 27.98
Weighted average remaining contractual life outstanding, beginning balance		4.9	5.8	6.7
Aggregate intrinsic value, outstanding, beginning balance	142.2	29.7	6.0
Aggregate intrinsic value, exercised	48.4	50.3	3.4
Aggregate intrinsic value, outstanding, ending balance	76.3	142.2	29.7
Share under option, option exercisable	2,220,000
Weighted average exercise price, options exercisable	$ 29.36
Weighted average remaining contractual life option exercisable	4.1
Aggregate intrinsic value, option exercisable	76.3
Proceeds from stock based compensation - gross	28.6	55.4	9.4
Tax benefit (loss)	24.4	11.7	(0.7)
Proceeds from stock based compensation - net	$ 53.0	$ 67.1	$ 8.7