Postretirement Benefit Plans (Summary of Plan Assets, Benefit Obligation and Funded Status) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 679	$ 691
Projected benefit obligation	(1,085)	(1,199)
Unfunded status of the plans	(406)	(508)
Amounts recognized in the balance sheet
Other non-current assets	48	27
Accrued and other current liabilities	(16)	(16)
Accrued post-retirement benefits	(438)	(519)
Net amount recognized	(406)	(508)
Accumulated other comprehensive income:
Net actuarial losses	(343)	(427)
Prior service credit	3	6
Total	(340)	(421)
Pension
Defined Benefit Plan Disclosure
Fair value of plan assets	679	691
Projected benefit obligation	(1,043)	(1,155)
Unfunded status of the plans	(364)	(464)
Amounts recognized in the balance sheet
Other non-current assets	48	27
Accrued and other current liabilities	(13)	(13)
Accrued post-retirement benefits	(399)	(478)
Net amount recognized	(364)	(464)
Accumulated other comprehensive income:
Net actuarial losses	(326)	(409)
Prior service credit	(4)	(3)
Total	(330)	(412)
Other Benefits
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Projected benefit obligation	(42)	(44)	$ (49)
Unfunded status of the plans	(42)	(44)
Amounts recognized in the balance sheet
Other non-current assets	0	0
Accrued and other current liabilities	(3)	(3)
Accrued post-retirement benefits	(39)	(41)
Net amount recognized	(42)	(44)
Accumulated other comprehensive income:
Net actuarial losses	(17)	(18)
Prior service credit	7	9
Total	(10)	(9)
Level 1
Defined Benefit Plan Disclosure
Fair value of plan assets	50	43
Level 2
Defined Benefit Plan Disclosure
Fair value of plan assets	185	188
Level 3
Defined Benefit Plan Disclosure
Fair value of plan assets	368	384	$ 13
NAV Practical Expedient
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 76	$ 76