Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	PREFERRED STOCK	COMMON STOCK	ADDITIONAL PAID-IN CAPITAL	RETAINED EARNINGS	RETAINED EARNINGS Cumulative Effect, Period of Adoption, Adjustment	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	TREASURY STOCK
Beginning balance at Dec. 31, 2019	$ 11,091.0	$ (10.1)	$ 1,273.4	$ 408.6	$ 1,013.1	$ 11,656.7	$ (10.1)	$ (194.7)	$ (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)
Dividends [Abstract]
Common stock dividends (in usd per share)	$ 0.70
Beginning balance at Dec. 31, 2019	$ 11,091.0	$ (10.1)	1,273.4	408.6	1,013.1	11,656.7	$ (10.1)	(194.7)	(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
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)
Dividends [Abstract]
Common stock dividends (in usd per share)	$ 0.70
Beginning balance at Dec. 31, 2020	$ 11,688.3		884.9	408.6	963.6	12,207.7		428.0	(3,204.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	375.1					375.1
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	(362.1)							(362.1)
Dividends [Abstract]
Common Stock	(151.0)					(151.0)
Preferred Stock	(16.2)					(16.2)
Stock Awards and Options Exercised	59.4				(49.5)				108.9
Stock Purchased	(135.6)								(135.6)
Ending balance at Mar. 31, 2021	$ 11,457.9		884.9	408.6	914.1	12,415.6		65.9	(3,231.2)
Dividends [Abstract]
Common stock dividends (in usd per share)	$ 0.70
Beginning balance at Dec. 31, 2020	$ 11,688.3		884.9	408.6	963.6	12,207.7		428.0	(3,204.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	743.2
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	(233.3)
Dividends [Abstract]
Stock Purchased	(165.8)
Ending balance at Jun. 30, 2021	11,823.0		884.9	408.6	921.1	12,630.9		194.7	(3,217.2)
Beginning balance at Mar. 31, 2021	11,457.9		884.9	408.6	914.1	12,415.6		65.9	(3,231.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	368.1					368.1
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	128.8							128.8
Dividends [Abstract]
Common Stock	(148.1)					(148.1)
Preferred Stock	(4.7)					(4.7)
Stock Awards and Options Exercised	51.2				7.0				44.2
Stock Purchased	(30.2)								(30.2)
Ending balance at Jun. 30, 2021	$ 11,823.0		$ 884.9	$ 408.6	$ 921.1	$ 12,630.9		$ 194.7	$ (3,217.2)
Dividends [Abstract]
Common stock dividends (in usd per share)	$ 0.70