Stock Incentive Plans (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
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	1,900,000
Status of Stock Options
Shares outstanding under option, beginning balance	2,220,000	3,253,000	5,177,000
Shares outstanding under option, exercised	(784,000)	(1,033,000)	(1,888,000)
Shares outstanding under option, forfeited			(36,000)
Shares outstanding under option, ending balance	1,436,000	2,220,000	3,253,000	5,177,000
Weighted average exercise price, beginning balance	$ 29.36	$ 28.64	$ 27.98
Weighted average exercise price, exercised	$ 26.86	$ 27.15	$ 26.73
Weighted average exercise price, forfeited			$ 33.95
Weighted average exercise price, ending balance	$ 30.65	$ 29.36	$ 28.64	$ 27.98
Weighted average remaining contractual life outstanding, beginning balance		4 years 1 month	4 years 11 months	5 years 9 months
Aggregate intrinsic value, outstanding, beginning balance	$ 76.3	$ 142.2	$ 29.7
Aggregate intrinsic value, exercised	40.1	48.4	50.3
Aggregate intrinsic value, outstanding, ending balance	58.8	76.3	142.2	29.7
Share under option, option exercisable	1,436,000
Weighted average exercise price, options exercisable	$ 30.65
Weighted average remaining contractual life option exercisable	3 years 5 months
Aggregate intrinsic value, option exercisable	58.8
Proceeds from stock based compensation - gross	20.9	28.6	55.4
Tax benefit (loss)	31.1	24.4	11.7
Proceeds from stock based compensation - net	$ 52.0	$ 53.0	$ 67.1
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	3 years 5 months