Retirement Benefits (Components of the Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 31	$ 34	$ 76
Interest cost	487	463	497
Expected return on plan assets	(863)	(864)	(921)
Amortization of prior service (credit) cost		(2)	(2)
Recognized actuarial loss (gain)	104	146	167
Net periodic benefit (credit) cost	(241)	(223)	(183)
Curtailment (gain) loss	0	0	(1)
Settlement loss	7	42	54
Total (credit) cost	(234)	(181)	(130)
Post-retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	1	1
Interest cost	3	3	4
Expected return on plan assets	0	0	0
Amortization of prior service (credit) cost	(2)	(2)	1
Recognized actuarial loss (gain)	(1)	(1)	0
Net periodic benefit (credit) cost	0	1	6
Curtailment (gain) loss	0	0	0
Settlement loss	0	0	0
Total (credit) cost	0	1	6
U.S. | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Interest cost	241	235	264
Expected return on plan assets	(343)	(357)	(357)
Amortization of prior service (credit) cost	0	0	0
Recognized actuarial loss (gain)	44	55	37
Net periodic benefit (credit) cost	(58)	(67)	(56)
U.S. | Post-retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1	1	2
Expected return on plan assets	0	0	0
Amortization of prior service (credit) cost	0	0	3
Recognized actuarial loss (gain)	(1)	(1)	(1)
Net periodic benefit (credit) cost	0	0	4
Non-U.S. | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	31	34	76
Interest cost	246	228	233
Expected return on plan assets	(520)	(507)	(564)
Amortization of prior service (credit) cost	0	(2)	(2)
Recognized actuarial loss (gain)	60	91	130
Net periodic benefit (credit) cost	(183)	(156)	(127)
Curtailment (gain) loss	0	0	(1)
Settlement loss	7	42	54
Total (credit) cost	(176)	(114)	(74)
Non-U.S. | Post-retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	1	1
Interest cost	2	2	2
Expected return on plan assets	0	0	0
Amortization of prior service (credit) cost	(2)	(2)	(2)
Recognized actuarial loss (gain)	0	0	1
Net periodic benefit (credit) cost	0	1	2
Curtailment (gain) loss	0	0	0
Settlement loss	0	0	0
Total (credit) cost	$ 0	$ 1	$ 2