Employee Benefit Plans (Reconciliations of Plan assets and the Projected Benefit Obligation, the Weighted-Average Assumptions Used to Determine Year-End Benefit Obligations, and the Amounts Recognized in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020		Dec. 31, 2019
Fair value of plan assets at January 1		$ 3,349
Fair value of plan assets at December 31		3,454	$ 3,349
Actuarial (gain) loss	[1]	159	128		$ 157
Qualified Plan
Fair value of plan assets at January 1		3,350	2,933
Actual return on plan assets		291	537	[2]	579	[2]
Plan participants' contributions		0	0
Benefits paid		(179)	(120)
Fair value of plan assets at December 31		3,462	3,350		2,933
Projected benefit obligation at January 1		2,327	2,131
Projected benefit obligation at December 31		2,214	2,327		2,131
Service cost	[3]	38	32	[2]	31	[2]
Interest cost		61	70	[2]	80	[2]
Actuarial (gain) loss		(69)	214
Plan participants' contributions		0	0
Plan amendments	[4]	36	0
Accumulated benefit obligation		2,199	2,312
Funded Status at December 31	[5],[6]	$ 1,248	$ 1,023
Weighted-average assumptions, discount rate, percent		2.96%	2.71%
Weighted-average assumptions, rate of compensation increase, percent		4.00%	4.00%
Actuarial net loss	[7]	$ (205)	$ (392)
Prior service credit	[7]	48	103
Balance at December 31	[7]	$ (157)	$ (289)
Qualified Plan | Minimum
Weighted-average assumptions, interest credit rating		379.00%	379.00%
Qualified Plan | Maximum
Weighted-average assumptions, interest credit rating		500.00%	500.00%
Non-Qualified Plan
Fair value of plan assets at January 1		$ 0
Benefits paid		(15)	$ (14)
Fair value of plan assets at December 31		0	0
Projected benefit obligation at January 1		252	235
Projected benefit obligation at December 31		207	252		235
Service cost	[3]	2	1		3
Interest cost		7	8		9
Actuarial (gain) loss		(3)	22
Plan participants' contributions		0	0
Plan amendments	[4]	(36)	0
Accumulated benefit obligation		204	251
Funded Status at December 31	[5],[6]	$ (207)	$ (252)
Weighted-average assumptions, discount rate, percent		2.96%	2.71%
Weighted-average assumptions, rate of compensation increase, percent		4.00%	4.00%
Actuarial net loss	[7]	$ (92)	$ (106)
Prior service credit	[7]	47	17
Balance at December 31	[7]	$ (45)	$ (89)
Non-Qualified Plan | Minimum
Weighted-average assumptions, interest credit rating		379.00%	379.00%
Non-Qualified Plan | Maximum
Weighted-average assumptions, interest credit rating		500.00%	500.00%
Postretirement Benefit Plan
Fair value of plan assets at January 1		$ 57	$ 57
Actual return on plan assets		(1)	3		5
Plan participants' contributions		1	1
Benefits paid		(4)	(4)
Fair value of plan assets at December 31		53	57		57
Projected benefit obligation at January 1		35	48
Projected benefit obligation at December 31		31	35		48
Service cost		0	0
Interest cost		1	1		$ 2
Actuarial (gain) loss		(1)	(11)
Plan participants' contributions		1	1
Plan amendments	[4]	(1)	0
Accumulated benefit obligation		31	35
Funded Status at December 31	[5],[6]	$ 22	$ 22
Weighted-average assumptions, discount rate, percent		2.79%	2.43%
Healthcare cost trend rate assumed for next year			6.00%
Rate to which the healthcare cost trend rate is assumed to decline (the ultimate trend rate), percent		4.50%	4.50%		4.50%
Year when healthcare cost trend rate reaches the ultimate trend rate			2027
Actuarial net loss	[7]	$ (11)	$ (9)
Prior service credit	[7]	2	1
Balance at December 31	[7]	$ (9)	$ (8)

[1] Balances at beginning and end of period, net of tax, and changes for the years ended December 31, 2020 and 2019 have been recast to reflect the retrospective application of the Corporation's election to change the accounting method for certain components of the qualified defined benefit pension plan as of January 1, 2021. Refer to Note 1 for further information.

[2] Recast to reflect the retrospective application of the Corporation's election to change the accounting method for certain components of defined pension benefit credit, effective January 1, 2021. For 2020, expected return on plan assets increased $14 million and amortization of net loss was reduced by $16 million, resulting in an increase of $30 million to total other components of net benefit credit. For 2019, expected return on plan assets increased $6 million, resulting in a corresponding increase to total other components of net benefit credit.

[3] Included in salaries and benefits expense on the Consolidated Statements of Income.

[4] The qualified defined benefit pension plan was amended in 2021 to include a flat dollar benefit for specified participants that would otherwise have been payable from the non-qualified defined benefit pension plan, resulting in a shift in projected benefit obligation from the non-qualified plan to the qualified plan.

[5] Based on projected benefit obligation for defined benefit pension plans and accumulated benefit obligation for postretirement benefit plan.

[6] The Corporation recognizes the overfunded and underfunded status of the plans in accrued income and other assets and accrued expenses and other liabilities, respectively, on the Consolidated Balance Sheets.

[7] The qualified defined benefit pension plan for the year ending December 31, 2020 has been recast to reflect the retrospective application of the Corporation's election to change the accounting method for certain components of defined pension benefit credit, effective January 1, 2021. For further information, refer to Note 1.