Employee Benefit Plans (Status of Prepaid Benefits Costs and Accrued Benefit Liabilities Included in Other Assets and Other Liabilities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits
Change in benefit obligation
Benefit obligation at the beginning of period	$ (15,483)	$ (14,637)
Service cost	(328)	(321)	$ (291)
Interest cost	(364)	(429)	(489)
Plan participants’ contributions	0	0
Medicare Part D subsidy receipts	0	0
Amendments	0	0
Curtailments	0	16
Actuarial gains (losses), net	310	(978)
Settlements	24	43
Special termination benefits	(1)	(7)
Benefits paid	868	878
Acquisition/Divestiture	13	46
Foreign currency changes and other	174	(94)
Benefit obligation at end of period	(14,787)	(15,483)	(14,637)
Change in plan assets
Plan assets at beginning of period	14,897	13,906
Actual return on plan assets	1,059	1,740
Employer contributions	205	200
Plan participants’ contributions	0	0
Disbursement for settlements	(24)	(43)
Benefits paid	(868)	(878)
Acquisition/Divestiture	(5)	(51)
Foreign currency changes and other	(22)	23
Plan assets at end of period	15,242	14,897	13,906
Funded status at end of period	455	(586)
Amounts recognized in the Statements of Financial Position
Prepaid benefit cost	3,272	2,426
Accrued benefit liability	(2,817)	(3,012)
Net amount recognized	455	(586)
Items recorded in “Accumulated other comprehensive income (loss)” not yet recognized as a component of net periodic (benefit) cost:
Prior service cost	(5)	(10)
Net actuarial loss	3,131	3,972
Net amount not recognized	3,126	3,962
Accumulated benefit obligation	(13,969)	(14,690)
Other Postretirement Benefits
Change in benefit obligation
Benefit obligation at the beginning of period	(2,040)	(1,993)
Service cost	(27)	(24)	(22)
Interest cost	(49)	(64)	(78)
Plan participants’ contributions	(23)	(22)
Medicare Part D subsidy receipts	(5)	(7)
Amendments	121	0
Curtailments	0	0
Actuarial gains (losses), net	55	(101)
Settlements	0	0
Special termination benefits	0	0
Benefits paid	173	171
Acquisition/Divestiture	0	0
Foreign currency changes and other	2	0
Benefit obligation at end of period	(1,793)	(2,040)	(1,993)
Change in plan assets
Plan assets at beginning of period	1,589	1,557
Actual return on plan assets	174	171
Employer contributions	8	10
Plan participants’ contributions	23	22
Disbursement for settlements	0	0
Benefits paid	(173)	(171)
Acquisition/Divestiture	0	0
Foreign currency changes and other	0	0
Plan assets at end of period	1,621	1,589	$ 1,557
Funded status at end of period	(172)	(451)
Amounts recognized in the Statements of Financial Position
Prepaid benefit cost	0	0
Accrued benefit liability	(172)	(451)
Net amount recognized	(172)	(451)
Items recorded in “Accumulated other comprehensive income (loss)” not yet recognized as a component of net periodic (benefit) cost:
Prior service cost	(69)	59
Net actuarial loss	211	354
Net amount not recognized	142	413
Accumulated benefit obligation	$ (1,793)	$ (2,040)