Retirement Benefits (Summary of Changes in the Fair Value of the Plans Level 3 Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 334	$ 372
Purchases	17	20
Sales	(14)	(19)
Unrealized Gain/ (Loss)	72	(5)
Realized Gain/ (Loss)	1	1
Exchange Rate Impact	(9)	(14)
Transfers in/(out) and Other (a)	282	(21)
Ending balance	683	334
Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	333	350
Purchases	17	20
Sales	(14)	(19)
Unrealized Gain/ (Loss)	72	(5)
Realized Gain/ (Loss)	1	1
Exchange Rate Impact	(9)	(14)
Transfers in/(out) and Other (a)	282	0
Ending balance	682	333
Corporate stocks
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	1	2
Purchases	0	0
Sales	0	0
Unrealized Gain/ (Loss)	0	0
Realized Gain/ (Loss)	0	0
Exchange Rate Impact	0	0
Transfers in/(out) and Other (a)	0	(1)
Ending balance	1	1
Corporate obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0	20
Purchases	0	0
Sales	0	0
Unrealized Gain/ (Loss)	0	0
Realized Gain/ (Loss)	0	0
Exchange Rate Impact	0	0
Transfers in/(out) and Other (a)	0	(20)
Ending balance	$ 0	$ 0