Retirement Benefits (Reconciliation of Prior Service Credit) (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 credit:
Total recognized as component of net periodic benefit credit	$ (222)	$ (234)	$ (181)
Post-retirement Benefits
Recognized as component of net periodic benefit credit:
Total recognized as component of net periodic benefit credit	1	0	1
Non-U.S. | Pension  Benefits
Recognized as component of net periodic benefit credit:
Total recognized as component of net periodic benefit credit	(162)	(176)	(114)
Non-U.S. | Post-retirement Benefits
Recognized as component of net periodic benefit credit:
Total recognized as component of net periodic benefit credit	0	0	1
Non-U.S. | Prior Service Credit (Cost) | Pension  Benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(2)	(2)
Recognized as component of net periodic benefit credit:
Amortization of prior service credit	0	0
Total recognized as component of net periodic benefit credit	0	0
Plan amendments	(11)	1
Exchange rate adjustments	0	(1)
Ending balance	(13)	(2)	(2)
Non-U.S. | Prior Service Credit (Cost) | Post-retirement Benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	11	12
Recognized as component of net periodic benefit credit:
Amortization of prior service credit	(2)	(2)
Total recognized as component of net periodic benefit credit	(2)	(2)
Plan amendments	0	0
Exchange rate adjustments	0	1
Ending balance	$ 9	$ 11	$ 12