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
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	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	736.5
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	293.9
Ending balance at Jun. 30, 2019	10,805.5			882.0		408.6		1,013.8		11,225.5			(159.8)		(2,564.6)
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
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	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)
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
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	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	673.9
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	565.1
Dividends [Abstract]
Stock Purchased	(297.0)
Ending balance at Jun. 30, 2020	11,382.2			884.9		408.6		951.5		11,988.4			370.4		(3,221.6)
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
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	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)