Retirement Benefits - Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Effect of Change in Interest Method on Service and Interest Cost Components	$ (145)		$ (435)
U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	128	$ 147	383	$ 440
Interest cost	381	454	1,143	1,363
Expected return on assets	(673)	(732)	(2,020)	(2,196)
Amortization of prior service costs/(credits)	43	38	128	116
Net remeasurement (gain)/loss	0	0	0	0
Separation programs/other	6	4	9	6
Net periodic benefit cost/(income)	(115)	(89)	(357)	(271)
Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	116	133	358	401
Interest cost	190	236	587	707
Expected return on assets	(329)	(372)	(1,018)	(1,116)
Amortization of prior service costs/(credits)	9	13	28	36
Net remeasurement (gain)/loss	0	0	11	0
Separation programs/other	16	11	88	30
Net periodic benefit cost/(income)	2	21	54	58
Worldwide OPEB
Defined Benefit Plan Disclosure [Line Items]
Service cost	13	15	37	45
Interest cost	49	59	146	178
Expected return on assets	0	0	0	0
Amortization of prior service costs/(credits)	(35)	(51)	(106)	(154)
Net remeasurement (gain)/loss	0	0	0	0
Separation programs/other	(1)	0	(1)	1
Net periodic benefit cost/(income)	26	$ 23	76	$ 70
Defined Benefit Plan, Estimated Future Employer Contributions To Funded Plans in Current Fiscal Year	1,200		1,200
Defined Benefit Plan Estimated Future Employer Discretionary Contributions In Next Fiscal Year			100
Defined Benefit Plan Change In Estimated Future Employer Contributions To Funded Plans in Current Fiscal Year	(300)		(300)
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	$ 1,500		1,500
Pension and Other Postretirement Benefit Contributions			800
Pension and Other Postretirement Benefit Contributions Unfunded Plans			$ 200