Employee Benefit Plans (Net Periodic Benefit Costs and Other Changes Recognized in OCI) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Other changes in plan assets and benefit obligations recognized in OCI:
Total recognized in OCI	$ 88	$ (279)	$ (328)
Pension Benefits
Net periodic benefit costs [Abstract]
Service costs	143	187	215
Interest costs	474	328	342
Settlement and curtailment (gains) losses	6	5	(7)
Expected return on plan assets	(480)	(516)	(506)
Amortization of net actuarial (gains) losses	159	129	162
Amortization of prior service costs (credit)	(11)	(11)	(12)
Total net periodic benefit costs (credit)	291	122	194
Other changes in plan assets and benefit obligations recognized in OCI:
Net actuarial (gains) losses	250	2	(166)
Prior service costs (credit)	0	8	1
Amortization of net actuarial (gains) losses	(159)	(129)	(162)
Amortization of prior service (costs) credit	11	11	12
Settlement and curtailment (gains) losses	(6)	(5)	(10)
Total recognized in OCI	94	(120)	(333)
Total recognized in net periodic benefit costs and OCI	385	2	(139)
Pension Benefits | Accumulated Other Comprehensive Income (Loss) Foreign Currency Translation Adjustments
Other changes in plan assets and benefit obligations recognized in OCI:
Total recognized in OCI	(2)	(7)	(8)
Other Postretirement Benefits
Net periodic benefit costs [Abstract]
Service costs	3	4	4
Interest costs	43	34	37
Settlement and curtailment (gains) losses	0	0	1
Expected return on plan assets	(54)	(55)	(56)
Amortization of net actuarial (gains) losses	(30)	(25)	(39)
Amortization of prior service costs (credit)	0	0	0
Total net periodic benefit costs (credit)	(38)	(42)	(53)
Other changes in plan assets and benefit obligations recognized in OCI:
Net actuarial (gains) losses	(41)	(191)	(54)
Prior service costs (credit)	0	0	(1)
Amortization of net actuarial (gains) losses	30	25	39
Amortization of prior service (costs) credit	0	0	0
Settlement and curtailment (gains) losses	0	0	10
Total recognized in OCI	(11)	(166)	(6)
Total recognized in net periodic benefit costs and OCI	(49)	(208)	(59)
Other Postretirement Benefits | Accumulated Other Comprehensive Income (Loss) Foreign Currency Translation Adjustments
Other changes in plan assets and benefit obligations recognized in OCI:
Total recognized in OCI	$ 0	$ 0	$ 0