Retirement Benefits (Reconciliation of Net Actuarial Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension  Benefits
Recognized as component of net periodic benefit cost (credit):
Total recognized as component of net periodic benefit cost (credit)	$ (222)	$ (234)	$ (181)
Post-retirement Benefits
Recognized as component of net periodic benefit cost (credit):
Total recognized as component of net periodic benefit cost (credit)	1	0	1
U.S. | Pension  Benefits
Recognized as component of net periodic benefit cost (credit):
Other	0	(49)
U.S. | Post-retirement Benefits
Recognized as component of net periodic benefit cost (credit):
Other	1	0
U.S. | Net Actuarial (Loss) Gain | Pension  Benefits
Reconciliation of unrecognized net actuarial gain loss [Roll Forward]
Beginning balance	(2,114)	(1,896)
Recognized as component of net periodic benefit cost (credit):
Amortization of net loss	72	44
Liability experience	(650)	(753)
Asset experience	246	491
Total amount recognized as change in plan assets and benefit obligations	(404)	(262)
Ending balance	(2,446)	(2,114)	(1,896)
U.S. | Net Actuarial (Loss) Gain | Post-retirement Benefits
Reconciliation of unrecognized net actuarial gain loss [Roll Forward]
Beginning balance	4	6
Recognized as component of net periodic benefit cost (credit):
Amortization of net loss	0	(1)
Liability experience	(1)	(1)
Asset experience	0	0
Total amount recognized as change in plan assets and benefit obligations	(1)	(1)
Ending balance	3	4	6
Non-U.S. | Pension  Benefits
Recognized as component of net periodic benefit cost (credit):
Total recognized as component of net periodic benefit cost (credit)	(162)	(176)	(114)
Non-U.S. | Post-retirement Benefits
Recognized as component of net periodic benefit cost (credit):
Total recognized as component of net periodic benefit cost (credit)	0	0	1
Non-U.S. | Net Actuarial (Loss) Gain | Pension  Benefits
Reconciliation of unrecognized net actuarial gain loss [Roll Forward]
Beginning balance	(3,055)	(2,568)
Recognized as component of net periodic benefit cost (credit):
Amortization of net loss	89	60
Effect of settlement	3	7
Total recognized as component of net periodic benefit cost (credit)	92	67
Liability experience	(1,273)	(1,339)
Asset experience	916	847
Total amount recognized as change in plan assets and benefit obligations	(357)	(492)
Exchange rate adjustments	(147)	(62)
Ending balance	(3,467)	(3,055)	(2,568)
Non-U.S. | Net Actuarial (Loss) Gain | Post-retirement Benefits
Reconciliation of unrecognized net actuarial gain loss [Roll Forward]
Beginning balance	(5)	(1)
Recognized as component of net periodic benefit cost (credit):
Amortization of net loss	0	0
Effect of settlement	0	0
Total recognized as component of net periodic benefit cost (credit)	0	0
Liability experience	(10)	(3)
Asset experience	0	0
Total amount recognized as change in plan assets and benefit obligations	(10)	(3)
Exchange rate adjustments	(1)	(1)
Ending balance	$ (16)	$ (5)	$ (1)