Income Taxes - Income Taxes Included in Income Statement (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Currently payable:
Federal	$ 423	$ 336	$ 241
State	73	83	20
Total currently payable	496	419	261
Deferred:
Federal	119	(156)	34
State	27	(36)	19
Total deferred	146	(192)	53
Total income tax expense (benefit)	642	227	314
Income tax (benefit) expense on securities transactions	(2)	1	5
Equity and gross receipts based taxes assessed in lieu of income tax recorded in noninterest expense	$ 33	$ 30	$ 23