CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Restatement Adjustment	Retained Earnings	Retained Earnings Restatement Adjustment	Treasury Stock
Increase (Decrease) in Stockholders' Equity
Cumulative Effect of New Accounting Principle in Period of Adoption				$ 0.0		$ 0.0
Balance at Beginning of Year at Dec. 31, 2016		$ 30.4	$ 2,272.8	(51.0)	$ (51.0)	8,744.0	$ 8,744.0	$ (2,028.2)
Increase (Decrease) in Stockholders' Equity
Common Stock Activity		0.1	30.5
Other Comprehensive Income (Loss)	$ 178.5			178.5
Net Income	994.2					994.2
Dividends to Stockholders (per common share: $1.09; $0.98; $0.86)						(196.0)
Purchases of Treasury Stock								(400.4)
Balance at End of Year at Dec. 31, 2017	9,574.9	30.5	2,303.3	127.5	110.0	9,542.2	9,556.7	(2,428.6)
Increase (Decrease) in Stockholders' Equity
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2016-01				(17.5)		14.5
Common Stock Activity		0.0	18.4
Other Comprehensive Income (Loss)	(924.2)			(924.2)
Net Income	523.4					523.4
Dividends to Stockholders (per common share: $1.09; $0.98; $0.86)						(217.0)
Purchases of Treasury Stock								(350.7)
Balance at End of Year at Dec. 31, 2018	8,621.8	30.5	2,321.7	(814.2)	$ (814.2)	9,863.1	$ 9,859.7	(2,779.3)
Increase (Decrease) in Stockholders' Equity
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2016-02				0.0		(3.4)
Common Stock Activity		0.1	26.4
Other Comprehensive Income (Loss)	851.5			851.5
Net Income	1,100.3					1,100.3
Dividends to Stockholders (per common share: $1.09; $0.98; $0.86)						(231.3)
Purchases of Treasury Stock								(400.4)
Balance at End of Year at Dec. 31, 2019	$ 9,965.0	$ 30.6	$ 2,348.1	$ 37.3		$ 10,728.7		$ (3,179.7)