Stock Incentive Plans - Restricted Stock (Details) (Restricted Stock [Member], USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock expense	$ 20.7	$ 25.8	$ 21.2
Restricted stock expense, net of tax	$ 15.1	$ 18.8	$ 15.5
Status of nonvested restricted stock [Roll Forward]
Nonvested shares subject to restriction, beginning balance	1,411,000	2,064,000	2,860,000
Nonvested shares subject to restriction, weighted average price, beginning balance	$ 37.86	$ 29.39	$ 19.51
Nonvested shares subject to restriction, granted	447,000	782,000	676,000
Nonvested shares subject to restriction, weighted average price, granted	$ 54.36	$ 37.82	$ 39.21
Nonvested shares subject to restriction, vested	(530,000)	(1,322,000)	(1,350,000)
Nonvested shares subject to restriction, weighted average price, vested	$ 37.42	$ 24.36	$ 13.72
Nonvested shares subject to restriction, forfeited	(62,000)	(113,000)	(122,000)
Nonvested shares subject to restriction, weighted average price, forfeited	$ 41.14	$ 36.59	$ 27.18
Nonvested shares subject to restriction, ending balance	1,266,000	1,411,000	2,064,000
Nonvested shares subject to restriction, weighted average price, ending balance	$ 43.57	$ 37.86	$ 29.39
Management [Member]
Status of nonvested restricted stock [Roll Forward]
Nonvested shares subject to restriction, granted	427,770
Director [Member]
Status of nonvested restricted stock [Roll Forward]
Nonvested shares subject to restriction, granted	18,730