Benefit Plans (Projected Benefit Obligations, Plan Assets and Funded Status of Pension Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Change in plan assets:
Accrued pension costs	$ (130)	$ (133)
Accrued postretirement health care costs	(1,079)	(1,083)
Pension [Member]
Change in benefit obligation:
Benefit obligation at beginning of year	6,292	8,544
Service cost	39	64	$ 68
Interest cost	333	206	184
Benefits paid	(460)	(462)
Actuarial (gains) losses	224	(2,060)
Plan amendments	0	0
Benefit obligation at end of year	6,428	6,292	8,544
Change in plan assets:
Fair value of plan assets at beginning of year	6,603	8,793
Actual return on plan assets	612	(1,748)
Employer contributions	20	20
Benefits paid	(460)	(462)
Fair value of plan assets at end of year	6,775	6,603	8,793
Funded status at December 31	347	311
Other assets	506	469
Other accrued liabilities	(29)	(25)
Accrued pension costs	(130)	(133)
Accrued postretirement health care costs	0	0
Defined benefit plan, amounts for asset (liability) recognized in statement of financial position	347	311
Postretirement Benefit Plan [Member]
Change in benefit obligation:
Benefit obligation at beginning of year	1,275	1,688
Service cost	15	23	20
Interest cost	65	41	38
Benefits paid	(96)	(87)
Actuarial (gains) losses	(10)	(392)
Plan amendments	(3)	2
Benefit obligation at end of year	1,246	1,275	1,688
Change in plan assets:
Fair value of plan assets at beginning of year	122	185
Actual return on plan assets	13	(35)
Employer contributions	0	0
Benefits paid	(33)	(28)
Fair value of plan assets at end of year	102	122	$ 185
Funded status at December 31	(1,144)	(1,153)
Other assets	0	0
Other accrued liabilities	(65)	(70)
Accrued pension costs	0	0
Accrued postretirement health care costs	(1,079)	(1,083)
Defined benefit plan, amounts for asset (liability) recognized in statement of financial position	$ (1,144)	$ (1,153)