Share Incentive Plans (Details 2) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Information regarding options outstanding and exercisable
Options Outstanding, Options	7,030,620
Options Outstanding, Weighted Average Remaining Contractual Life in Years	5 years 6 months 24 days
Options Outstanding, Weighted Average Exercise Price	$ 46.16
Options Exercisable, Options	5,011,784
Options Exercisable, Weighted Average Exercise Price	$ 42.18
Options, Vested and expected to vest	6,590,486
Options, Weighted Average Remaining Contractual Life in Years	5 years 4 months 2 days
Options, Weighted Average Exercise Price	$ 45.50
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 18.70
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 62.32
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value	$ 180.5
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 148.7
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	4 years 7 months 5 days
Market value of common shares	$ 71.84
Exercise Price Range One [Member]
Information regarding options outstanding and exercisable
Options Outstanding, Options	988,826
Options Outstanding, Weighted Average Remaining Contractual Life in Years	4 years 1 month 2 days
Options Outstanding, Weighted Average Exercise Price	$ 23.07
Options Exercisable, Options	988,826
Options Exercisable, Weighted Average Exercise Price	$ 23.07
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 18.70
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 24.93
Exercise Price Range Two [Member]
Information regarding options outstanding and exercisable
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 24.94
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 31.16
Exercise Price Range Three [Member]
Information regarding options outstanding and exercisable
Options Outstanding, Options	1,091,358
Options Outstanding, Weighted Average Remaining Contractual Life in Years	3 years 7 months 11 days
Options Outstanding, Weighted Average Exercise Price	$ 32.61
Options Exercisable, Options	1,091,358
Options Exercisable, Weighted Average Exercise Price	$ 32.61
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 31.17
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 37.39
Exercise Price Range Four [Member]
Information regarding options outstanding and exercisable
Options Outstanding, Options	702,568
Options Outstanding, Weighted Average Remaining Contractual Life in Years	2 years 4 months 10 days
Options Outstanding, Weighted Average Exercise Price	$ 40.12
Options Exercisable, Options	702,568
Options Exercisable, Weighted Average Exercise Price	$ 40.12
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 37.40
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 43.62
Exercise Price Range Five [Member]
Information regarding options outstanding and exercisable
Options Outstanding, Options	24,628
Options Outstanding, Weighted Average Remaining Contractual Life in Years	5 years 9 months 29 days
Options Outstanding, Weighted Average Exercise Price	$ 48.63
Options Exercisable, Options	24,628
Options Exercisable, Weighted Average Exercise Price	$ 48.63
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 43.63
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 49.86
Exercise Price Range Six [Member]
Information regarding options outstanding and exercisable
Options Outstanding, Options	2,343,836
Options Outstanding, Weighted Average Remaining Contractual Life in Years	6 years 2 months 15 days
Options Outstanding, Weighted Average Exercise Price	$ 53.93
Options Exercisable, Options	1,387,110
Options Exercisable, Weighted Average Exercise Price	$ 53.85
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 49.87
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 56.09
Exercise Price Range Seven [Member]
Information regarding options outstanding and exercisable
Options Outstanding, Options	1,879,404
Options Outstanding, Weighted Average Remaining Contractual Life in Years	7 years 10 months 13 days
Options Outstanding, Weighted Average Exercise Price	$ 58.72
Options Exercisable, Options	817,294
Options Exercisable, Weighted Average Exercise Price	$ 59.84
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 56.10
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 62.32