Employee Benefit Plans (Reconciliation of Changes in Projected Benefit Obligation and Change in Plan Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, beginning balance	$ 5,400
Fair value of plan assets, end balance	5,615	$ 5,400
Pension Plans | Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation at end of year	4,601	4,517
Projected benefit obligation at beginning of year	4,543	5,423
Service cost	130	142	$ 133
Interest cost	249	156	139
Amendments
Actuarial (gains)/losses and changes in assumptions	45	(833)
Benefits paid	(326)	(345)
Projected benefit obligation at end of year	4,641	4,543	5,423
Fair value of plan assets, beginning balance	5,400	6,788
Actual return on plan assets	541	(1,043)
Benefits paid	(326)	(345)
Fair value of plan assets, end balance	5,615	5,400	6,788
Funded status	974	857
Noncurrent asset	974	857
Net amount recognized on the consolidated balance sheet	974	857
Prior service cost (credit)	11	14
Net actuarial loss (gain)	148	322
Amount recognized in AOCI	159	336
Pension Plans | Nonqualified Plan
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation at end of year	212	219
Projected benefit obligation at beginning of year	222	280
Service cost	3	3	4
Interest cost	11	7	6
Actuarial (gains)/losses and changes in assumptions	3	(44)
Benefits paid	(22)	(24)
Projected benefit obligation at end of year	217	222	280
Fair value of plan assets, beginning balance
Employer contribution	22	24
Benefits paid	(22)	(24)
Fair value of plan assets, end balance
Funded status	(217)	(222)
Current liability	(23)	(24)
Noncurrent liability	(194)	(198)
Net amount recognized on the consolidated balance sheet	(217)	(222)
Net actuarial loss (gain)	33	31
Amount recognized in AOCI	33	31
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation at beginning of year	260	326
Service cost	3	4	4
Interest cost	14	9	8
Actuarial (gains)/losses and changes in assumptions	7	(57)
Participant contributions	2	2
Federal Medicare subsidy on benefits paid		1
Benefits paid	(25)	(25)
Projected benefit obligation at end of year	261	260	326
Fair value of plan assets, beginning balance	242	263
Actual return on plan assets	16	(21)
Employer contribution	22	22
Participant contributions	2	2
Federal Medicare subsidy on benefits paid		1
Benefits paid	(25)	(25)
Fair value of plan assets, end balance	257	242	$ 263
Funded status	(4)	(18)
Noncurrent asset	26	10
Current liability	(3)	(3)
Noncurrent liability	(27)	(25)
Net amount recognized on the consolidated balance sheet	(4)	(18)
Prior service cost (credit)	1	1
Net actuarial loss (gain)	(31)	(32)
Amount recognized in AOCI	$ (30)	$ (31)