Retirement Benefits (Components of the Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension  Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 36	$ 31	$ 34
Interest cost	421	487	463
Expected return on plan assets	(844)	(863)	(864)
Amortization of prior service (credit)			(2)
Recognized actuarial loss (gain)	161	104	146
Net periodic benefit (credit) cost	(226)	(241)	(223)
Plan termination	1	0	0
Settlement loss	3	7	42
Total (credit) cost	(222)	(234)	(181)
Post-retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	1
Interest cost	3	3	3
Expected return on plan assets	0	0	0
Amortization of prior service (credit)	(2)	(2)	(2)
Recognized actuarial loss (gain)	0	(1)	(1)
Net periodic benefit (credit) cost	1	0	1
Plan termination	0	0	0
Settlement loss	0	0	0
Total (credit) cost	1	0	1
U.S. | Pension  Benefits
Defined Benefit Plan Disclosure [Line Items]
Interest cost	213	241	235
Expected return on plan assets	(345)	(343)	(357)
Recognized actuarial loss (gain)	72	44	55
Net periodic benefit (credit) cost	(60)	(58)	(67)
U.S. | Post-retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1	1	1
Expected return on plan assets	0	0	0
Recognized actuarial loss (gain)	0	(1)	(1)
Net periodic benefit (credit) cost	1	0	0
Non-U.S. | Pension  Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	36	31	34
Interest cost	208	246	228
Expected return on plan assets	(499)	(520)	(507)
Amortization of prior service (credit)	0	0	(2)
Recognized actuarial loss (gain)	89	60	91
Net periodic benefit (credit) cost	(166)	(183)	(156)
Plan termination	1	0	0
Settlement loss	3	7	42
Total (credit) cost	(162)	(176)	(114)
Non-U.S. | Post-retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	1
Interest cost	2	2	2
Expected return on plan assets	0	0	0
Amortization of prior service (credit)	(2)	(2)	(2)
Recognized actuarial loss (gain)	0	0	0
Net periodic benefit (credit) cost	0	0	1
Plan termination	0	0	0
Settlement loss	0	0	0
Total (credit) cost	$ 0	$ 0	$ 1