Equity Incentive Plan (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Aggregate Intrinsic Value [Abstract]
Options, Outstanding, Intrinsic Value	$ 243.7	$ 208.9
Options, Exercisable, Intrinsic Value	$ 209.8
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Outstanding, Number, Beginning	2,104,775
Options, Grants in Period, Net of Forfeitures	135,858
Options, Exercises in Period	(352,602)
Options, Forfeitures in Period	(16,337)
Options, Outstanding, Number, Ending	1,871,694
Options, Exercisable, Number	1,377,919
Weighted Average Exercise Price [Abstract]
Options, Outstanding, Weighted Average Exercise Price, Beginning	$ 94.45
Options, Grants in Period, Weighted Average Exercise Price	$ 244.99
Options, Exercises in Period, Weighted Average Exercise Price	$ 56.00
Options, Forfeitures in Period, Weighted Average Exercise Price	$ 115.04
Options, Outstanding, Weighted Average Exercise Price, Ending	$ 112.57
Options, Exercisable, Weighted Average Exercise Price	$ 90.35