Pension and Postretirement Benefit Plans - Change in Benefit Obligation and Plan Assets and Amounts Recognized in Balance Sheet and AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
​Amounts recognized in the Consolidated Balance Sheet as of December 31, (Millions)
Non-current assets	$ 1,253	$ 1,225
Accrued benefit cost
Current liabilities	(79)	(77)
Non-current liabilities	(2,471)	(1,966)
U.S. Pension Plans
Change in plan assets
Company contributions	143	155
Postretirement Benefits
Change in benefit obligation
Benefit obligation at beginning of year	1,797	2,281
Acquisitions/Transfers	0	0
Service cost	27	42	$ 53
Interest cost	87	52	43
Participant contributions	0	0
Foreign exchange rate changes	10	1
Plan amendments	0	0
Actuarial (gain) loss	124	(458)
Benefit payments	(142)	(115)
Settlements, curtailments, special termination benefits and other	(6)	(6)
Benefit obligation at end of year	1,897	1,797	2,281
Change in plan assets
Fair value of plan assets at beginning of year	1,017	1,353
Acquisitions/Transfers	0	0
Actual return on plan assets	102	(218)
Company contributions	9	3
Participant contributions	0	0
Foreign exchange rate changes	0	0
Benefit payments	(142)	(115)
Settlements, curtailments, special termination benefits and other	(6)	(6)
Fair value of plan assets at end of year	980	1,017	1,353
Funded status at end of year	(917)	(780)
​Amounts recognized in the Consolidated Balance Sheet as of December 31, (Millions)
Non-current assets	0	0
Accrued benefit cost
Current liabilities	(15)	(11)
Non-current liabilities	(902)	(769)
Ending balance	(917)	(780)
Amounts recognized in accumulated other comprehensive income as of December 31, (Millions)
Net transition obligation (asset)	0	0
Net actuarial loss (gain)	423	332
Prior service cost (credit)	(135)	(166)
Ending balance	288	166
United States | U.S. Pension Plans
Change in benefit obligation
Benefit obligation at beginning of year	13,505	18,104
Acquisitions/Transfers	0	0
Service cost	171	256	286
Interest cost	662	417	360
Participant contributions	0	0
Foreign exchange rate changes	0	0
Plan amendments	0	0
Actuarial (gain) loss	779	(3,777)
Benefit payments	(1,504)	(1,495)
Settlements, curtailments, special termination benefits and other	(115)	0
Benefit obligation at end of year	13,498	13,505	18,104
Change in plan assets
Fair value of plan assets at beginning of year	12,648	16,953
Acquisitions/Transfers	0	0
Actual return on plan assets	1,144	(2,875)
Company contributions	60	65
Participant contributions	0	0
Foreign exchange rate changes	0	0
Benefit payments	(1,504)	(1,495)
Settlements, curtailments, special termination benefits and other	0	0
Fair value of plan assets at end of year	12,348	12,648	16,953
Funded status at end of year	(1,150)	(857)
​Amounts recognized in the Consolidated Balance Sheet as of December 31, (Millions)
Non-current assets	0	0
Accrued benefit cost
Current liabilities	(52)	(52)
Non-current liabilities	(1,098)	(805)
Ending balance	(1,150)	(857)
Amounts recognized in accumulated other comprehensive income as of December 31, (Millions)
Net transition obligation (asset)	0	0
Net actuarial loss (gain)	4,809	4,616
Prior service cost (credit)	(17)	(56)
Ending balance	4,792	4,560
Accumulated benefit obligation	13,073	12,967
Plans with accumulated benefit obligation in excess of plan assets
Accumulated benefit obligation	13,073	402
Fair value of plan assets	12,348	0
Plans with projected benefit obligation in excess of plan assets
Projected benefit obligation	13,498	13,505
Fair value of plan assets	12,348	12,648
International | U.S. Pension Plans
Change in benefit obligation
Benefit obligation at beginning of year	5,072	7,942
Acquisitions/Transfers	0	0
Service cost	76	128	164
Interest cost	225	125	98
Participant contributions	9	7
Foreign exchange rate changes	208	(567)
Plan amendments	(1)	8
Actuarial (gain) loss	298	(2,240)
Benefit payments	(258)	(266)
Settlements, curtailments, special termination benefits and other	(58)	(65)
Benefit obligation at end of year	5,571	5,072	7,942
Change in plan assets
Fair value of plan assets at beginning of year	5,891	8,016
Acquisitions/Transfers	0	0
Actual return on plan assets	426	(1,286)
Company contributions	82	90
Participant contributions	9	7
Foreign exchange rate changes	241	(602)
Benefit payments	(258)	(266)
Settlements, curtailments, special termination benefits and other	(50)	(68)
Fair value of plan assets at end of year	6,341	5,891	$ 8,016
Funded status at end of year	770	819
​Amounts recognized in the Consolidated Balance Sheet as of December 31, (Millions)
Non-current assets	1,253	1,225
Accrued benefit cost
Current liabilities	(12)	(14)
Non-current liabilities	(471)	(392)
Ending balance	770	819
Amounts recognized in accumulated other comprehensive income as of December 31, (Millions)
Net transition obligation (asset)	3	4
Net actuarial loss (gain)	316	157
Prior service cost (credit)	9	10
Ending balance	328	171
Accumulated benefit obligation	5,275	4,814
Plans with accumulated benefit obligation in excess of plan assets
Accumulated benefit obligation	1,145	775
Fair value of plan assets	761	427
Plans with projected benefit obligation in excess of plan assets
Projected benefit obligation	1,272	851
Fair value of plan assets	$ 793	$ 442