Options Outstanding and Exercisable - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Information regarding options outstanding and exercisable
Options Outstanding, Options	6,023,101
Options Outstanding, Weighted Average Remaining Contractual Life in Years	4 years 7 months 29 days
Options Outstanding, Weighted Average Exercise Price	$ 42.05
Options Exercisable, Options	5,610,677
Options Exercisable, Weighted Average Exercise Price	$ 40.91
Options, Vested and expected to vest	6,003,870
Options, Weighted Average Remaining Contractual Life in Years	4 years 6 months 20 days
Options, Weighted Average Exercise Price	$ 41.97
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	19.67
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 68.55
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value	$ 135.3
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 132.0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	4 years 4 months 26 days
Market value of common shares	$ 64.36
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number		4,436,990	5,011,784
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price		$ 45.11	$ 42.18
Exercise Price Range One [Member]
Information regarding options outstanding and exercisable
Options Outstanding, Options	892,111
Options Outstanding, Weighted Average Remaining Contractual Life in Years	2 years 1 month 7 days
Options Outstanding, Weighted Average Exercise Price	$ 19.67
Options Exercisable, Options	892,111
Options Exercisable, Weighted Average Exercise Price	$ 19.67
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	19.67
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
Options Outstanding, Options	930,884
Options Outstanding, Weighted Average Remaining Contractual Life in Years	2 years 6 months 15 days
Options Outstanding, Weighted Average Exercise Price	$ 29.42
Options Exercisable, Options	930,884
Options Exercisable, Weighted Average Exercise Price	$ 29.42
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	$ 37.39
Exercise Price Range Three [Member]
Information regarding options outstanding and exercisable
Options Outstanding, Options	2,412
Options Outstanding, Weighted Average Remaining Contractual Life in Years	3 years 10 months
Options Outstanding, Weighted Average Exercise Price	$ 41.44
Options Exercisable, Options	2,412
Options Exercisable, Weighted Average Exercise Price	$ 41.44
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 Four [Member]
Information regarding options outstanding and exercisable
Options Outstanding, Options	2,715,880
Options Outstanding, Weighted Average Remaining Contractual Life in Years	5 years 6 months
Options Outstanding, Weighted Average Exercise Price	$ 46.59
Options Exercisable, Options	2,515,401
Options Exercisable, Weighted Average Exercise Price	$ 46.47
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 Five [Member]
Information regarding options outstanding and exercisable
Options Outstanding, Options	1,114,654
Options Outstanding, Weighted Average Remaining Contractual Life in Years	5 years 1 month 28 days
Options Outstanding, Weighted Average Exercise Price	$ 51.30
Options Exercisable, Options	1,114,654
Options Exercisable, Weighted Average Exercise Price	$ 51.30
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 Six [Member]
Information regarding options outstanding and exercisable
Options Outstanding, Options	2,761
Options Outstanding, Weighted Average Remaining Contractual Life in Years	8 years 5 months 24 days
Options Outstanding, Weighted Average Exercise Price	$ 60.80
Options Exercisable, Options	2,761
Options Exercisable, Weighted Average Exercise Price	$ 60.80
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
Exercise Price Range Seven [Member]
Information regarding options outstanding and exercisable
Options Outstanding, Options	364,399
Options Outstanding, Weighted Average Remaining Contractual Life in Years	8 years 6 months 27 days
Options Outstanding, Weighted Average Exercise Price	$ 66.77
Options Exercisable, Options	152,454
Options Exercisable, Weighted Average Exercise Price	$ 67.27
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	62.33
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 68.55