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			22.4
Other Comprehensive Income (Loss)	$ 175.3			175.3
Recognition and Measurement of Financial Assets and Financial Liabilities, Reclassification from AOCI to Retained Earnings				0.0	0.0
Net Income (Loss)	727.3				727.3
Dividends to Stockholders (per common share: $0.72; $0.63)					(144.1)
Purchases of Treasury Stock	(300.3)					(300.3)
Balance at End of Period at Sep. 30, 2017	9,448.6	30.4	2,295.2	124.3	9,327.2	(2,328.5)
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			11.0
Other Comprehensive Income (Loss)	(978.5)			(978.5)
Recognition and Measurement of Financial Assets and Financial Liabilities, Reclassification from AOCI to Retained Earnings	(17.5)			(17.5)	14.5
Net Income (Loss)	274.3				274.3
Dividends to Stockholders (per common share: $0.72; $0.63)					(160.2)
Purchases of Treasury Stock	(200.3)					(200.3)
Balance at End of Period at Sep. 30, 2018	$ 8,518.2	$ 30.5	$ 2,314.3	$ (868.5)	$ 9,670.8	$ (2,628.9)