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
Balance, beginning of period at Dec. 31, 2017	$ 10,216.2	$ (4.5)		$ 882.0		$ 408.6		$ 1,047.2		$ 9,685.1	$ (4.5)		$ (414.3)		$ (1,392.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification of Certain Tax Effects from AOCI	0.0									25.3			(25.3)
Net Income	1,556.4									1,556.4
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	(14.1)												(14.1)
Dividends – Common Stock	(439.1)									(439.1)
Preferred Stock	(46.4)									(46.4)
Stock Awards and Options Exercised	164.1							21.3							142.8
Stock Purchased	(924.3)														(924.3)
Balance, end of period 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	1,492.2									1,492.2
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	259.0												259.0
Dividends – Common Stock	(565.9)									(565.9)
Preferred Stock	(46.4)									(46.4)
Issuance of Preferred Stock, Series E	391.4			391.4
Stock Awards and Options Exercised	152.6							(55.4)							208.0
Stock Purchased	(1,100.2)														(1,100.2)
Balance, end of period 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]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Net Income	$ 1,209.3									1,209.3
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	622.7												622.7
Dividends – Common Stock	(592.0)									(592.0)
Preferred Stock	(44.7)									(44.7)
Redemption of Preferred Stock, Series C	(400.0)			(388.5)						(11.5)
Stock Awards and Options Exercised	111.9							(49.5)							161.4
Stock Purchased	(299.8)														(299.8)
Balance, end of period at Dec. 31, 2020	$ 11,688.3			$ 884.9		$ 408.6		$ 963.6		$ 12,207.7			$ 428.0		$ (3,204.5)