Retirement Benefits - Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Effect of Change in Interest Method on Service and Interest Cost Components	$ (145)
U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	128	$ 147
Interest cost	381	454
Expected return on assets	(673)	(732)
Amortization of prior service costs/(credits)	42	39
Net remeasurement (gain)/loss	0	0
Separation programs/other	0	2
Settlements and curtailments	0	0
Net periodic benefit cost/(income)	(122)	(90)
Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	118	135
Interest cost	195	239
Expected return on assets	(339)	(375)
Amortization of prior service costs/(credits)	10	12
Net remeasurement (gain)/loss	0	0
Separation programs/other	7	7
Settlements and curtailments	0	0
Net periodic benefit cost/(income)	(9)	18
Worldwide OPEB
Defined Benefit Plan Disclosure [Line Items]
Service cost	12	15
Interest cost	48	60
Expected return on assets	0	0
Amortization of prior service costs/(credits)	(35)	(51)
Net remeasurement (gain)/loss	0	0
Separation programs/other	0	0
Settlements and curtailments	0	0
Net periodic benefit cost/(income)	25	$ 24
Defined Benefit Plan, Estimated Future Employer Contributions To Funded Plans in Current Fiscal Year	1,500
Defined Benefit Plan Estimated Future Employer Discretionary Contributions In Next Fiscal Year	400
Pension And Other Postretirement Expected Benefit Contributions Unfunded Plans	300
Pension and Other Postretirement Benefit Contributions and Expected Future Employer Contributions To Funded and Unfunded Plans	1,800
Pension and Other Postretirement Benefit Contributions	400
Pension and Other Postretirement Benefit Contributions Unfunded Plans	$ 100