Basis of Presentation (Adoption of ASU No. 2016-09) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
New Accounting Pronouncement, Early Adoption [Line Items]
Provision for Income Taxes	$ (114.8)	$ (113.8)
Net Income	276.1	245.4
Earnings Allocated to Participating Securities	4.5	4.1
Net Income Applicable to Common Stock	$ 255.4	$ 239.5
Effective Tax Rate	29.40%	31.70%
Basic Earnings per Share	$ 1.10	$ 1.03
Diluted Earnings per Share	$ 1.09	$ 1.03
Diluted Weighted Average Shares Outstanding (000s)	230,630,876	229,797,945
Additional Paid-In Capital	$ 1,010.2		$ 1,035.8
Retained Earnings	$ 9,074.4		$ 8,908.4
Accounting Standards Update 2016-09
New Accounting Pronouncement, Early Adoption [Line Items]
Provision for Income Taxes		$ 3.6
Accounting Standards Update 2016-09 | As Reported
New Accounting Pronouncement, Early Adoption [Line Items]
Provision for Income Taxes		117.4
Net Income		241.8
Earnings Allocated to Participating Securities		4.1
Net Income Applicable to Common Stock		$ 235.9
Effective Tax Rate		32.70%
Basic Earnings per Share		$ 1.01
Diluted Earnings per Share		$ 1.01
Diluted Weighted Average Shares Outstanding (000s)		229,980,000
Additional Paid-In Capital		$ 1,022.1
Retained Earnings		8,394.8
Accounting Standards Update 2016-09 | As Adjusted
New Accounting Pronouncement, Early Adoption [Line Items]
Provision for Income Taxes		113.8
Net Income		245.4
Earnings Allocated to Participating Securities		4.1
Net Income Applicable to Common Stock		$ 239.5
Effective Tax Rate		31.70%
Basic Earnings per Share		$ 1.03
Diluted Earnings per Share		$ 1.03
Diluted Weighted Average Shares Outstanding (000s)		229,798,000
Additional Paid-In Capital		$ 1,018.5
Retained Earnings		$ 8,398.4