Retirement Benefits - Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
U.S. Plans
Change in Benefit Obligation
Benefit obligation at January 1	$ 44,936	$ 47,103
Service cost	510	586	$ 507
Interest cost	1,524	1,817
Amendments	0	99
Separation programs and other	(30)	(27)
Curtailments	0	0
Settlements	0	0
Plan participant contributions	27	26
Benefits paid	(2,966)	(2,949)
Foreign exchange translation	0	0
Actuarial (gain)/loss	1,745	(1,719)
Benefit obligation at December 31	45,746	44,936	47,103
Change in Plan Assets
Fair value of plan assets at January 1	41,252	44,844
Actual return on plan assets	3,538	(755)
Company contributions	130	130
Plan participant contributions	27	26
Benefits paid	(2,966)	(2,949)
Settlements	0	0
Foreign exchange translation	0	0
Defined Benefit Plan Other Increase Decrease Plan Assets	(42)	(44)
Fair value of plan assets at December 31	41,939	41,252	44,844
Funded status at December 31	(3,807)	(3,684)
Amounts Recognized on the Balance Sheet
Prepaid assets	0	0
Accrued liabilities	(3,807)	(3,684)
Total	(3,807)	(3,684)
Amounts Recognized in Accumulated Other Comprehensive Loss (pre-tax)
Unamortized prior service costs/(credits)	383	553
Pension Plans in which Accumulated Benefit Obligation Exceeds Plan Assets at December 31
Accumulated benefit obligation	26,170	26,021
Fair value of plan assets	23,204	22,967
Accumulated Benefit Obligation at December 31	44,513	43,698
Pension Plans in which Projected Benefit Obligation Exceeds Plan Assets at December 31
Projected benefit obligation	45,746	44,936
Fair value of plan assets	41,939	41,252
Expected Future Benefit Payments and Amortization
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	3,030
Defined Benefit Plan, Expected Future Benefit Payments, Year Two	3,020
Defined Benefit Plan, Expected Future Benefit Payments, Year Three	2,980
Defined Benefit Plan, Expected Future Benefit Payments, Year Four	2,970
Defined Benefit Plan, Expected Future Benefit Payments, Year Five	2,950
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Year Thereafter	14,750
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Prior service cost/(credit) expected to be recognized	143
Non-U.S. Plans
Change in Benefit Obligation
Benefit obligation at January 1	29,639	33,223
Service cost	483	532	468
Interest cost	782	936
Amendments	0	4
Separation programs and other	71	40
Curtailments	2	0
Settlements	(131)	(29)
Plan participant contributions	22	24
Benefits paid	(1,252)	(1,350)
Foreign exchange translation	(2,576)	(2,995)
Actuarial (gain)/loss	3,584	(746)
Benefit obligation at December 31	30,624	29,639	33,223
Change in Plan Assets
Fair value of plan assets at January 1	25,141	25,675
Actual return on plan assets	3,041	1,722
Company contributions	1,346	1,345
Plan participant contributions	22	24
Benefits paid	(1,252)	(1,350)
Settlements	(131)	(29)
Foreign exchange translation	(2,612)	(2,238)
Defined Benefit Plan Other Increase Decrease Plan Assets	(6)	(8)
Fair value of plan assets at December 31	25,549	25,141	25,675
Funded status at December 31	(5,075)	(4,498)
Amounts Recognized on the Balance Sheet
Prepaid assets	1,515	1,611
Accrued liabilities	(6,590)	(6,109)
Total	(5,075)	(4,498)
Amounts Recognized in Accumulated Other Comprehensive Loss (pre-tax)
Unamortized prior service costs/(credits)	213	278
Pension Plans in which Accumulated Benefit Obligation Exceeds Plan Assets at December 31
Accumulated benefit obligation	10,039	9,634
Fair value of plan assets	4,700	4,636
Accumulated Benefit Obligation at December 31	27,166	26,835
Pension Plans in which Projected Benefit Obligation Exceeds Plan Assets at December 31
Projected benefit obligation	11,703	11,238
Fair value of plan assets	5,113	5,129
Expected Future Benefit Payments and Amortization
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	1,170
Defined Benefit Plan, Expected Future Benefit Payments, Year Two	1,080
Defined Benefit Plan, Expected Future Benefit Payments, Year Three	1,100
Defined Benefit Plan, Expected Future Benefit Payments, Year Four	1,120
Defined Benefit Plan, Expected Future Benefit Payments, Year Five	1,130
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Year Thereafter	5,980
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Prior service cost/(credit) expected to be recognized	35
Worldwide OPEB [Member]
Change in Benefit Obligation
Benefit obligation at January 1	5,701	6,375
Service cost	49	60	54
Interest cost	194	236
Amendments	14	1
Separation programs and other	0	1
Curtailments	0	0
Settlements	0	0
Plan participant contributions	20	23
Benefits paid - Worldwide OPEB	(382)	(402)
Foreign exchange translation	49	(301)
Actuarial (gain)/loss	220	(292)
Benefit obligation at December 31	5,865	5,701	6,375
Change in Plan Assets
Fair value of plan assets at January 1	0	0
Actual return on plan assets	0	0
Company contributions	0	0
Plan participant contributions	20	23
Plan participant contributions - Worldwide OPEB	0	0
Benefits paid - Worldwide OPEB	0	0
Settlements	0	0
Foreign exchange translation	0	0
Defined Benefit Plan Other Increase Decrease Plan Assets	0	0
Fair value of plan assets at December 31	0	0	$ 0
Funded status at December 31	(5,865)	(5,701)
Amounts Recognized on the Balance Sheet
Prepaid assets	0	0
Accrued liabilities	(5,865)	(5,701)
Total	(5,865)	(5,701)
Amounts Recognized in Accumulated Other Comprehensive Loss (pre-tax)
Unamortized prior service costs/(credits)	(322)	(475)
Plan Contributions [Abstract]
Pension and Other Postretirement Benefit Contributions	1,200
Pension and Other Postretirement Benefit Contributions Unfunded Plans	300
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year	1,000
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	1,300
Expected Future Benefit Payments and Amortization
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	350
Defined Benefit Plan, Expected Future Benefit Payments, Year Two	350
Defined Benefit Plan, Expected Future Benefit Payments, Year Three	350
Defined Benefit Plan, Expected Future Benefit Payments, Year Four	340
Defined Benefit Plan, Expected Future Benefit Payments, Year Five	340
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Year Thereafter	1,710
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Prior service cost/(credit) expected to be recognized	(119)
Fixed Income | U.S. Plans
Change in Plan Assets
Fair value of plan assets at January 1	31,665
Fair value of plan assets at December 31	31,002	31,665
Fixed Income | Non-U.S. Plans
Change in Plan Assets
Fair value of plan assets at January 1	13,971
Fair value of plan assets at December 31	14,667	13,971
Alternatives | U.S. Plans
Change in Plan Assets
Fair value of plan assets at January 1	6,451
Fair value of plan assets at December 31	6,643	6,451
Alternatives | Non-U.S. Plans
Change in Plan Assets
Fair value of plan assets at January 1	3,185
Fair value of plan assets at December 31	2,760	3,185
Hedge Funds [Member] | U.S. Plans
Change in Plan Assets
Fair value of plan assets at January 1	2,723
Fair value of plan assets at December 31	2,960	2,723
Hedge Funds [Member] | Non-U.S. Plans
Change in Plan Assets
Fair value of plan assets at January 1	1,870
Fair value of plan assets at December 31	1,598	1,870
Private Equity Funds [Member] | U.S. Plans
Change in Plan Assets
Fair value of plan assets at January 1	2,745
Fair value of plan assets at December 31	2,548	2,745
Private Equity Funds [Member] | Non-U.S. Plans
Change in Plan Assets
Fair value of plan assets at January 1	633
Fair value of plan assets at December 31	$ 679	$ 633