Stock Incentive Plans - Restricted Stock (Details) (Restricted Stock [Member], USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended			1 Months Ended
	Feb. 28, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Apr. 30, 2011 Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock expense		$ 21.2	$ 15.1	$ 18.9
Restricted stock expense, net of tax		$ 15.5	$ 11.4	$ 14.7
Status of nonvested restricted stock [Roll Forward]
Nonvested shares subject to restriction, beginning balance		1,430,000	1,871,000	1,547,000
Nonvested shares subject to restriction, weighted average price, beginning balance		$ 39.02	$ 30.55	$ 29.90
Nonvested shares subject to restriction, granted	328,138	338,000	274,000	603,000	9,677
Nonvested shares subject to restriction, weighted average price, granted		$ 78.41	$ 70.57	$ 36.16
Nonvested shares subject to restriction, vested		(675,000)	(609,000)	(188,000)
Nonvested shares subject to restriction, weighted average price, vested		$ 27.43	$ 27.39	$ 44.80
Nonvested shares subject to restriction, forfeited		(61,000)	(106,000)	(91,000)
Nonvested shares subject to restriction, weighted average price, forfeited		$ 54.35	$ 38.05	$ 27.10
Nonvested shares subject to restriction, ending balance		1,032,000	1,430,000	1,871,000
Nonvested shares subject to restriction, weighted average price, ending balance		$ 58.77	$ 39.02	$ 30.55