Retirement Benefits - Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Plan
Plan Contributions [Abstract]
Payment for Pension and Other Postretirement Benefits	$ 730
Defined Contribution Plan, Employer Discretionary Contribution Amount	140
Pension and Other Postretirement Benefit Contributions Unfunded Plans	342
Pension And Other Postretirement Expected Benefit Contributions Unfunded Plans	300
Pension Plan | Minimum
Plan Contributions [Abstract]
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	600
Pension Plan | Maximum
Plan Contributions [Abstract]
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	800
Pension Plan | U.S. Plans
Change in Benefit Obligation
Benefit obligation at January 1	42,269	$ 46,340
Service cost	474	544	$ 534
Interest cost	1,570	1,466	1,525
Amendments	0	0
Separation programs/other	(24)	9
Curtailments	0	(15)
Settlements	(966)	0
Plan participant contributions	23	25
Benefits paid	(2,615)	(2,880)
Foreign exchange translation	0	0
Actuarial (gain)/loss	4,941	(3,220)
Benefit obligation at December 31	45,672	42,269	46,340
Change in Plan Assets
Fair value of plan assets at January 1	39,774	44,160
Actual return on plan assets	7,800	(1,627)
Company contributions	284	140
Plan participant contributions	23	25
Benefits paid	(2,615)	(2,880)
Settlements	(966)	0
Foreign exchange translation	0	0
Defined Benefit Plan Other Increase Decrease Plan Assets	(47)	(44)
Fair value of plan assets at December 31	44,253	39,774	44,160
Funded status at December 31	(1,419)	(2,495)
Amounts Recognized on the Balance Sheet
Prepaid assets	911	165
Accrued liabilities	(2,330)	(2,660)
Total	(1,419)	(2,495)
Amounts Recognized in Accumulated Other Comprehensive Loss (pre-tax)
Unamortized prior service costs/(credits)	8	95
Pension Plans in which Accumulated Benefit Obligation Exceeds Plan Assets at December 31
Accumulated benefit obligation	2,141	1,965
Fair value of plan assets	156	137
Accumulated Benefit Obligation at December 31	44,578	41,312
Pension Plans in which Projected Benefit Obligation Exceeds Plan Assets at December 31
Projected benefit obligation	22,085	20,529
Fair value of plan assets	19,755	17,872
Expected Future Benefit Payments and Amortization
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	2,820
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	2,790
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	2,770
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	2,780
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	2,810
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Year Thereafter	13,970
Pension Plan | U.S. Plans | Alternatives
Change in Plan Assets
Fair value of plan assets at January 1	6,505
Fair value of plan assets at December 31	6,038	6,505
Pension Plan | U.S. Plans | Hedge Funds
Change in Plan Assets
Fair value of plan assets at January 1	3,217
Fair value of plan assets at December 31	2,961	3,217
Pension Plan | U.S. Plans | Private Equity Funds
Change in Plan Assets
Fair value of plan assets at January 1	2,046
Fair value of plan assets at December 31	1,884	2,046
Pension Plan | Non-U.S. Plans
Change in Benefit Obligation
Benefit obligation at January 1	31,079	34,098
Service cost	506	588	566
Interest cost	691	684	671
Amendments	10	135
Separation programs/other	391	97
Curtailments	(43)	(2)
Settlements	(272)	(16)
Plan participant contributions	17	19
Benefits paid	(1,395)	(1,316)
Foreign exchange translation	501	(1,858)
Actuarial (gain)/loss	3,888	(1,350)
Benefit obligation at December 31	35,373	31,079	34,098
Change in Plan Assets
Fair value of plan assets at January 1	27,273	29,657
Actual return on plan assets	2,935	21
Company contributions	789	629
Plan participant contributions	17	19
Benefits paid	(1,395)	(1,316)
Settlements	(330)	(16)
Foreign exchange translation	678	(1,708)
Defined Benefit Plan Other Increase Decrease Plan Assets	(9)	(13)
Fair value of plan assets at December 31	29,958	27,273	29,657
Funded status at December 31	(5,415)	(3,806)
Amounts Recognized on the Balance Sheet
Prepaid assets	2,318	3,161
Accrued liabilities	(7,733)	(6,967)
Total	(5,415)	(3,806)
Amounts Recognized in Accumulated Other Comprehensive Loss (pre-tax)
Unamortized prior service costs/(credits)	274	285
Pension Plans in which Accumulated Benefit Obligation Exceeds Plan Assets at December 31
Accumulated benefit obligation	12,421	10,904
Fair value of plan assets	5,948	5,232
Accumulated Benefit Obligation at December 31	32,106	27,787
Pension Plans in which Projected Benefit Obligation Exceeds Plan Assets at December 31
Projected benefit obligation	13,864	12,321
Fair value of plan assets	6,131	5,357
Expected Future Benefit Payments and Amortization
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	1,440
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	1,240
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	1,250
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	1,260
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	1,280
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Year Thereafter	6,670
Pension Plan | Non-U.S. Plans | Alternatives
Change in Plan Assets
Fair value of plan assets at January 1	2,243
Fair value of plan assets at December 31	2,227	2,243
Pension Plan | Non-U.S. Plans | Hedge Funds
Change in Plan Assets
Fair value of plan assets at January 1	1,143
Fair value of plan assets at December 31	1,207	1,143
Pension Plan | Non-U.S. Plans | Private Equity Funds
Change in Plan Assets
Fair value of plan assets at January 1	687
Fair value of plan assets at December 31	695	687
Worldwide OPEB
Change in Benefit Obligation
Benefit obligation at January 1	5,559	6,169
Service cost	43	54	49
Interest cost	211	195	197
Amendments	0	0
Separation programs/other	3	1
Curtailments	0	0
Settlements	0	0
Plan participant contributions	3	17
Benefits paid	(367)	(372)
Foreign exchange translation	69	(139)
Actuarial (gain)/loss	551	(366)
Benefit obligation at December 31	6,072	5,559	6,169
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 - 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	(6,072)	(5,559)
Amounts Recognized on the Balance Sheet
Prepaid assets	0	0
Accrued liabilities	(6,072)	(5,559)
Total	(6,072)	(5,559)
Amounts Recognized in Accumulated Other Comprehensive Loss (pre-tax)
Unamortized prior service costs/(credits)	29	$ 97
Expected Future Benefit Payments and Amortization
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	340
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	330
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	330
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	330
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	330
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Year Thereafter	$ 1,630