Share-Based Compensation (Details 3) - Nonvested stock awards - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Nonvested Stock Shares
Nonvested at the beginning of the period (in shares)	3,442,202
Granted (in shares)	1,406,569
Vested (in shares)	(1,188,908)
Forfeited (in shares)	(254,656)
Nonvested at the end of the period (in shares)	3,405,207	3,442,202
Nonvested Stock Shares, Weighted Average Grant Date Fair Value
Nonvested at the beginning of the period (in dollars per share)	$ 48.37
Granted (in dollars per share)	44.72
Vested (in dollars per share)	38.90
Forfeited (in dollars per share)	49.39
Nonvested at the end of the period (in dollars per share)	$ 50.09	$ 48.37
Compensation expense	$ 47.5	$ 54.1	$ 53.2
Related income tax benefit recognized	17.6	20.1	19.6
Remaining unamortized expense of nonvested stock expected to be recognized	$ 115.3
Period for expense amortized	2 years 4 months 24 days
Total fair value of shares vested	$ 53.9	$ 104.8	$ 80.5