Retirement Benefits - Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 134	$ 127	$ 267	$ 255
Interest cost	381	381	762	762
Expected return on assets	(684)	(674)	(1,367)	(1,347)
Amortization of prior service costs/(credits)	35	43	71	85
Net remeasurement (gain)/loss	0	0	0	0
Separation programs/other	9	3	12	3
Net periodic benefit cost/(income)	(125)	(120)	(255)	(242)
Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	125	124	259	242
Interest cost	173	202	332	397
Expected return on assets	(335)	(350)	(665)	(689)
Amortization of prior service costs/(credits)	9	9	18	19
Net remeasurement (gain)/loss	0	11	0	11
Separation programs/other	3	65	19	72
Net periodic benefit cost/(income)	(25)	61	(37)	52
Worldwide OPEB
Defined Benefit Plan Disclosure [Line Items]
Service cost	12	12	24	24
Interest cost	49	49	98	97
Expected return on assets	0	0	0	0
Amortization of prior service costs/(credits)	(29)	(36)	(59)	(71)
Net remeasurement (gain)/loss	0	0	0	0
Separation programs/other	0	0	0	0
Net periodic benefit cost/(income)	32	$ 25	63	$ 50
Defined Benefit Plan, Estimated Future Employer Contributions To Funded Plans in Current Fiscal Year	1,000		1,000
Pension And Other Postretirement Expected Benefit Contributions Unfunded Plans	300		300
Pension and Other Postretirement Benefit Contributions and Expected Future Employer Contributions To Funded and Unfunded Plans	$ 1,300		1,300
Pension and Other Postretirement Benefit Contributions			500
Pension and Other Postretirement Benefit Contributions Unfunded Plans			$ 150