Benefit Plans (Narrative) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Amounts charged to expense for defined contribution plans			$ 91,000,000	$ 90,000,000	$ 88,000,000
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation			6,100,000,000	8,200,000,000
Accumulated benefit obligation			134,000,000	176,000,000
Fair value of plan assets			0	0
Projected benefit obligation			158,000,000	227,000,000
Defined benefit plan, pension plan with projected benefit obligation in excess of plan assets, plan assets			0	0
Defined benefit plan, plan assets, amount			$ 6,603,000,000	$ 8,793,000,000	$ 8,911,000,000
Defined benefit plan, assumptions used calculating net periodic benefit cost, expected long-term rate of return on plan assets			6.10%	6.60%	6.60%
Pension [Member] | Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, assumptions used calculating net periodic benefit cost, expected long-term rate of return on plan assets		6.10%
Pension [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions			$ 30,000,000
Pension [Member] | Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Composition of plan assets			1.00%
Pension [Member] | Below Investment Grade [Member]
Defined Benefit Plan Disclosure [Line Items]
Composition of plan assets			10.00%
Pension [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation percentage			20.00%
Pension [Member] | Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation percentage			80.00%
Pension [Member] | Fixed Income Securities [Member] | Below Investment Grade [Member]
Defined Benefit Plan Disclosure [Line Items]
Composition of plan assets			13.00%
Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan amendments	$ 432,000,000
Defined benefit plan, plan assets, amount			$ 122,000,000	$ 185,000,000	$ 201,000,000
Defined benefit plan, assumptions used calculating net periodic benefit cost, expected long-term rate of return on plan assets			7.70%	7.70%	7.70%
Postretirement Benefit Plan [Member] | Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, assumptions used calculating net periodic benefit cost, expected long-term rate of return on plan assets		7.40%
Postretirement Benefit Plan [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions			$ 30,000,000
Postretirement Benefit Plan [Member] | Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount			$ 0
Postretirement Benefit Plan [Member] | Below Investment Grade [Member]
Defined Benefit Plan Disclosure [Line Items]
Composition of plan assets			5.00%
Postretirement Benefit Plan [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation percentage			55.00%
Postretirement Benefit Plan [Member] | Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation percentage			45.00%
Postretirement Benefit Plan [Member] | Fixed Income Securities [Member] | Below Investment Grade [Member]
Defined Benefit Plan Disclosure [Line Items]
Composition of plan assets			12.00%