Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Millions	Total	Cumulative Effect Adjustment	Adjusted Balance	PREFERRED STOCK	PREFERRED STOCK Adjusted Balance	COMMON STOCK	COMMON STOCK Adjusted Balance	ADDITIONAL PAID-IN CAPITAL	ADDITIONAL PAID-IN CAPITAL Adjusted Balance	RETAINED EARNINGS	RETAINED EARNINGS Cumulative Effect Adjustment	RETAINED EARNINGS Adjusted Balance	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) Adjusted Balance	TREASURY STOCK	TREASURY STOCK Adjusted Balance
Beginning balance at Dec. 31, 2018	$ 10,508.3			$ 882.0		$ 408.6		$ 1,068.5		$ 10,776.8			$ (453.7)		$ (2,173.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	347.1									347.1
Net Change	108.4												108.4
Dividends [Abstract]
Common Stock	(133.7)									(133.7)
Preferred Stock	(17.3)									(17.3)
Stock Awards and Options Exercised	60.8							(65.2)							126.0
Stock Purchased	(257.4)														(257.4)
Ending balance at Mar. 31, 2019	10,616.2			882.0		408.6		1,003.3		10,972.9			(345.3)		(2,305.3)
Beginning balance at Dec. 31, 2018	10,508.3			882.0		408.6		1,068.5		10,776.8			(453.7)		(2,173.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	1,121.1
Net Change	362.7
Ending balance at Sep. 30, 2019	10,811.3			882.0		408.6		1,009.7		11,441.2			(91.0)		(2,839.2)
Beginning balance at Mar. 31, 2019	10,616.2			882.0		408.6		1,003.3		10,972.9			(345.3)		(2,305.3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	389.4									389.4
Net Change	185.5												185.5
Dividends [Abstract]
Common Stock	(130.9)									(130.9)
Preferred Stock	(5.9)									(5.9)
Stock Awards and Options Exercised	22.4							10.5							11.9
Stock Purchased	(271.2)														(271.2)
Ending balance at Jun. 30, 2019	10,805.5			882.0		408.6		1,013.8		11,225.5			(159.8)		(2,564.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	384.6									384.6
Net Change	68.8												68.8
Dividends [Abstract]
Common Stock	(151.5)									(151.5)
Preferred Stock	(17.4)									(17.4)
Stock Awards and Options Exercised	28.5							(4.1)							32.6
Stock Purchased	(307.2)														(307.2)
Ending balance at Sep. 30, 2019	10,811.3			882.0		408.6		1,009.7		11,441.2			(91.0)		(2,839.2)
Beginning balance at Dec. 31, 2019	11,091.0	$ (10.1)	$ 11,080.9	1,273.4	$ 1,273.4	408.6	$ 408.6	1,013.1	$ 1,013.1	11,656.7	$ (10.1)	$ 11,646.6	(194.7)	$ (194.7)	(3,066.1)	$ (3,066.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	360.6									360.6
Net Change	239.7												239.7
Dividends [Abstract]
Common Stock	(148.6)									(148.6)
Preferred Stock	(19.0)									(19.0)
Redemption of Preferred Stock, Series C	(400.0)			(388.5)						(11.5)
Stock Awards and Options Exercised	62.9							(74.8)							137.7
Stock Purchased	(296.8)														(296.8)
Ending balance at Mar. 31, 2020	10,879.7			884.9		408.6		938.3		11,828.1			45.0		(3,225.2)
Beginning balance at Dec. 31, 2019	11,091.0	$ (10.1)	$ 11,080.9	1,273.4	$ 1,273.4	408.6	$ 408.6	1,013.1	$ 1,013.1	11,656.7	$ (10.1)	$ 11,646.6	(194.7)	$ (194.7)	(3,066.1)	$ (3,066.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	968.4
Net Change	619.2
Dividends [Abstract]
Stock Purchased	(298.5)
Ending balance at Sep. 30, 2020	11,579.1			884.9		408.6		961.8		12,118.3			424.5		(3,219.0)
Beginning balance at Mar. 31, 2020	10,879.7			884.9		408.6		938.3		11,828.1			45.0		(3,225.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	313.3									313.3
Net Change	325.4												325.4
Dividends [Abstract]
Common Stock	(148.2)									(148.2)
Preferred Stock	(4.8)									(4.8)
Stock Awards and Options Exercised	17.0							13.2							3.8
Stock Purchased	(0.2)														(0.2)
Ending balance at Jun. 30, 2020	11,382.2			884.9		408.6		951.5		11,988.4			370.4		(3,221.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	294.5									294.5
Net Change	54.1												54.1
Dividends [Abstract]
Common Stock	(148.4)									(148.4)
Preferred Stock	(16.2)									(16.2)
Stock Awards and Options Exercised	14.4							10.3							4.1
Stock Purchased	(1.5)														(1.5)
Ending balance at Sep. 30, 2020	$ 11,579.1			$ 884.9		$ 408.6		$ 961.8		$ 12,118.3			$ 424.5		$ (3,219.0)