Retirement Benefits - Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Worldwide OPEB
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
Service cost	$ 11	$ 11	$ 23	$ 22
Interest cost	41	52	84	105
Expected return on assets	0	0	0	0
Amortization of prior service costs/(credits)	(4)	(17)	(8)	(35)
Net remeasurement (gain)/loss	0	0	58	0
Separation programs/other	1	0	0	0
Settlements and curtailments	0	0	(2)	0
Net periodic benefit cost/(income)	49	46	155	92
Foreign Plan | Pension Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
Service cost	127	127	258	256
Interest cost	130	173	263	349
Expected return on assets	(254)	(281)	(521)	(567)
Amortization of prior service costs/(credits)	8	9	17	17
Net remeasurement (gain)/loss	(152)	0	(232)	0
Separation programs/other	33	232	57	244
Settlements and curtailments	17	0	18	0
Net periodic benefit cost/(income)	(91)	260	(140)	299
UNITED STATES | Pension Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
Service cost	130	114	260	228
Interest cost	323	409	646	818
Expected return on assets	(699)	(649)	(1,398)	(1,298)
Amortization of prior service costs/(credits)	1	21	2	43
Net remeasurement (gain)/loss	4	(10)	4	(10)
Separation programs/other	3	0	13	1
Settlements and curtailments	4	(50)	4	(50)
Net periodic benefit cost/(income)	$ (234)	$ (165)	$ (469)	$ (268)