Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions		Sep. 30, 2020	Dec. 31, 2019
Total allowance		$ 5,751.0	$ 2,742.0
Common stock, par value (in dollars per share)		$ 5	$ 5
Common stock, authorized (shares)		800,000,000	800,000,000
Common stock, issued (shares)		542,000,000	542,000,000
Common stock held in treasury at cost (shares)		118,000,000	109,000,000
Preferred stock (less than)	[1]
Preferred stock (less than)		0.5	$ 0.5
Portion at Fair Value, Fair Value Disclosure
Loans held for sale, fair value		1,400.0	1,100.0
Loans, fair value		1,300.0	700.0
Other assets, fair value		100.0	100.0
Other borrowed funds, fair value		$ 100.0	100.0
Cumulative Effect, Period of Adoption, Adjustment | Accounting Standards Update 2016-13
Total allowance			$ 463.0

[1] Par value less than $.5 million at each date.