Stock Incentive Plans - Restricted Stock (Details) (Restricted Stock [Member], USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock expense		$ 25.8	$ 21.2	$ 15.1
Restricted stock expense, net of tax		$ 18.8	$ 15.5	$ 11.4
Status of nonvested restricted stock [Roll Forward]
Nonvested shares subject to restriction, beginning balance	2,064,000	2,064,000	2,860,000	3,742,000
Nonvested shares subject to restriction, weighted average price, beginning balance	$ 29.39	$ 29.39	$ 19.51	$ 15.28
Nonvested shares subject to restriction, granted	746,394	782,000	676,000	548,000
Nonvested shares subject to restriction, weighted average price, granted		$ 37.82	$ 39.21	$ 35.28
Nonvested shares subject to restriction, vested		(1,322,000)	(1,350,000)	(1,218,000)
Nonvested shares subject to restriction, weighted average price, vested		$ 24.36	$ 13.72	$ 13.70
Nonvested shares subject to restriction, forfeited		(113,000)	(122,000)	(212,000)
Nonvested shares subject to restriction, weighted average price, forfeited		$ 36.59	$ 27.18	$ 19.02
Nonvested shares subject to restriction, ending balance		1,411,000	2,064,000	2,860,000
Nonvested shares subject to restriction, weighted average price, ending balance		$ 37.86	$ 29.39	$ 19.51
Director [Member]
Status of nonvested restricted stock [Roll Forward]
Nonvested shares subject to restriction, granted		28,280