CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Millions	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Treasury Stock
Balance at Beginning of Year at Dec. 31, 2016		$ 30.4	$ 2,272.8	$ (51.0)	$ 8,744.0	$ (2,028.2)
Increase (Decrease) in Stockholders' Equity
Common Stock Activity			10.1
Other Comprehensive Income (Loss)	$ 155.9			155.9
Recognition and Measurement of Financial Assets and Financial Liabilities, Reclassification from AOCI to Retained Earnings				0.0	0.0
Net Income	475.0				475.0
Dividends to Stockholders (per common share: $0.46; $0.40)					(92.3)
Purchases of Treasury Stock	(200.1)					(200.1)
Balance at End of Period at Jun. 30, 2017	9,316.6	30.4	2,282.9	104.9	9,126.7	(2,228.3)
Balance at Beginning of Year at Dec. 31, 2017	9,574.9	30.5	2,303.3	127.5	9,542.2	(2,428.6)
Increase (Decrease) in Stockholders' Equity
Common Stock Activity			5.3
Other Comprehensive Income (Loss)	(386.2)			(386.2)
Recognition and Measurement of Financial Assets and Financial Liabilities, Reclassification from AOCI to Retained Earnings	(17.5)			(17.5)	14.5
Net Income	559.0				559.0
Dividends to Stockholders (per common share: $0.46; $0.40)					(103.3)
Purchases of Treasury Stock	(200.3)					(200.3)
Balance at End of Period at Jun. 30, 2018	$ 9,446.4	$ 30.5	$ 2,308.6	$ (276.2)	$ 10,012.4	$ (2,628.9)