Postemployment benefit plans - Fair value of pension and other postretirement benefit plan assets, by category (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Plan | U.S. Pension Benefits
Defined Benefit Plan Disclosure
Plan assets	$ 12,738	$ 12,456	$ 17,227
Pension Plan | U.S. Pension Benefits | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	1,222	1,243
Pension Plan | U.S. Pension Benefits | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	913	950
Pension Plan | U.S. Pension Benefits | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	5,772	5,537
Pension Plan | U.S. Pension Benefits | Non-U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	1,228	1,244
Pension Plan | U.S. Pension Benefits | U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	2,988	2,904
Pension Plan | U.S. Pension Benefits | U.S. governmental agency
Defined Benefit Plan Disclosure
Plan assets	84	19
Pension Plan | U.S. Pension Benefits | Non-U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	100	118
Pension Plan | U.S. Pension Benefits | Real estate
Defined Benefit Plan Disclosure
Plan assets	3	8
Pension Plan | U.S. Pension Benefits | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	428	433
Pension Plan | U.S. Pension Benefits | Level 1
Defined Benefit Plan Disclosure
Plan assets	2,116	2,154
Pension Plan | U.S. Pension Benefits | Level 1 | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	1,107	1,098
Pension Plan | U.S. Pension Benefits | Level 1 | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	910	948
Pension Plan | U.S. Pension Benefits | Level 1 | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Level 1 | Non-U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Level 1 | U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Level 1 | U.S. governmental agency
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Level 1 | Non-U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Level 1 | Real estate
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Level 1 | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	99	108
Pension Plan | U.S. Pension Benefits | Level 2
Defined Benefit Plan Disclosure
Plan assets	10,149	9,779
Pension Plan | U.S. Pension Benefits | Level 2 | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	10	20
Pension Plan | U.S. Pension Benefits | Level 2 | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Level 2 | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	5,706	5,460
Pension Plan | U.S. Pension Benefits | Level 2 | Non-U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	1,228	1,244
Pension Plan | U.S. Pension Benefits | Level 2 | U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	2,988	2,904
Pension Plan | U.S. Pension Benefits | Level 2 | U.S. governmental agency
Defined Benefit Plan Disclosure
Plan assets	84	19
Pension Plan | U.S. Pension Benefits | Level 2 | Non-U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	100	118
Pension Plan | U.S. Pension Benefits | Level 2 | Real estate
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Level 2 | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	33	14
Pension Plan | U.S. Pension Benefits | Level 3
Defined Benefit Plan Disclosure
Plan assets	63	78
Pension Plan | U.S. Pension Benefits | Level 3 | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	24	26
Pension Plan | U.S. Pension Benefits | Level 3 | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	3	2
Pension Plan | U.S. Pension Benefits | Level 3 | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	33	40
Pension Plan | U.S. Pension Benefits | Level 3 | Non-U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Level 3 | U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Level 3 | U.S. governmental agency
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Level 3 | Non-U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Level 3 | Real estate
Defined Benefit Plan Disclosure
Plan assets	3	8
Pension Plan | U.S. Pension Benefits | Level 3 | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	0	2
Pension Plan | U.S. Pension Benefits | Measured at NAV
Defined Benefit Plan Disclosure
Plan assets	410	445
Pension Plan | U.S. Pension Benefits | Measured at NAV | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	81	99
Pension Plan | U.S. Pension Benefits | Measured at NAV | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Measured at NAV | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	33	37
Pension Plan | U.S. Pension Benefits | Measured at NAV | Non-U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Measured at NAV | U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Measured at NAV | U.S. governmental agency
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Measured at NAV | Non-U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Measured at NAV | Real estate
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Measured at NAV | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	296	309
Pension Plan | Non-U.S.  Pension Benefits
Defined Benefit Plan Disclosure
Plan assets	3,467	3,244	4,552
Pension Plan | Non-U.S.  Pension Benefits | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	73	61
Pension Plan | Non-U.S.  Pension Benefits | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	282	257
Pension Plan | Non-U.S.  Pension Benefits | Global equities
Defined Benefit Plan Disclosure
Plan assets	48	53
Pension Plan | Non-U.S.  Pension Benefits | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	91	186
Pension Plan | Non-U.S.  Pension Benefits | Non-U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	466	631
Pension Plan | Non-U.S.  Pension Benefits | U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	63	66
Pension Plan | Non-U.S.  Pension Benefits | Non-U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	998	1,273
Pension Plan | Non-U.S.  Pension Benefits | Global fixed income
Defined Benefit Plan Disclosure
Plan assets	307	330
Pension Plan | Non-U.S.  Pension Benefits | Real estate
Defined Benefit Plan Disclosure
Plan assets	219	198
Pension Plan | Non-U.S.  Pension Benefits | Insurance contracts
Defined Benefit Plan Disclosure
Plan assets	675
Pension Plan | Non-U.S.  Pension Benefits | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	245	189
Pension Plan | Non-U.S.  Pension Benefits | Level 1
Defined Benefit Plan Disclosure
Plan assets	383	367
Pension Plan | Non-U.S.  Pension Benefits | Level 1 | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	73	61
Pension Plan | Non-U.S.  Pension Benefits | Level 1 | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	228	208
Pension Plan | Non-U.S.  Pension Benefits | Level 1 | Global equities
Defined Benefit Plan Disclosure
Plan assets	28	26
Pension Plan | Non-U.S.  Pension Benefits | Level 1 | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Level 1 | Non-U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Level 1 | U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Level 1 | Non-U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Level 1 | Global fixed income
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Level 1 | Real estate
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Level 1 | Insurance contracts
Defined Benefit Plan Disclosure
Plan assets	0
Pension Plan | Non-U.S.  Pension Benefits | Level 1 | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	54	72
Pension Plan | Non-U.S.  Pension Benefits | Level 2
Defined Benefit Plan Disclosure
Plan assets	2,143	2,591
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	33	28
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | Global equities
Defined Benefit Plan Disclosure
Plan assets	0	10
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	91	186
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | Non-U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	466	631
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	63	66
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | Non-U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	998	1,273
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | Global fixed income
Defined Benefit Plan Disclosure
Plan assets	91	82
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | Real estate
Defined Benefit Plan Disclosure
Plan assets	210	198
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | Insurance contracts
Defined Benefit Plan Disclosure
Plan assets	0
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	191	117
Pension Plan | Non-U.S.  Pension Benefits | Level 3
Defined Benefit Plan Disclosure
Plan assets	675	0
Pension Plan | Non-U.S.  Pension Benefits | Level 3 | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Level 3 | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Level 3 | Global equities
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Level 3 | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Level 3 | Non-U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Level 3 | U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Level 3 | Non-U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Level 3 | Global fixed income
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Level 3 | Real estate
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Level 3 | Insurance contracts
Defined Benefit Plan Disclosure
Plan assets	675
Pension Plan | Non-U.S.  Pension Benefits | Level 3 | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Measured at NAV
Defined Benefit Plan Disclosure
Plan assets	266	286
Pension Plan | Non-U.S.  Pension Benefits | Measured at NAV | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Measured at NAV | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	21	21
Pension Plan | Non-U.S.  Pension Benefits | Measured at NAV | Global equities
Defined Benefit Plan Disclosure
Plan assets	20	17
Pension Plan | Non-U.S.  Pension Benefits | Measured at NAV | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Measured at NAV | Non-U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Measured at NAV | U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Measured at NAV | Non-U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Measured at NAV | Global fixed income
Defined Benefit Plan Disclosure
Plan assets	216	248
Pension Plan | Non-U.S.  Pension Benefits | Measured at NAV | Real estate
Defined Benefit Plan Disclosure
Plan assets	9	0
Pension Plan | Non-U.S.  Pension Benefits | Measured at NAV | Insurance contracts
Defined Benefit Plan Disclosure
Plan assets	0
Pension Plan | Non-U.S.  Pension Benefits | Measured at NAV | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	0	0
Other Postretirement  Benefits
Defined Benefit Plan Disclosure
Plan assets	144	102	$ 130
Other Postretirement  Benefits | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	70	43
Other Postretirement  Benefits | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	25	19
Other Postretirement  Benefits | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	30
Other Postretirement  Benefits | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	19	40
Other Postretirement  Benefits | Level 1
Defined Benefit Plan Disclosure
Plan assets	89	60
Other Postretirement  Benefits | Level 1 | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	65	41
Other Postretirement  Benefits | Level 1 | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	23	16
Other Postretirement  Benefits | Level 1 | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	0
Other Postretirement  Benefits | Level 1 | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	1	3
Other Postretirement  Benefits | Level 2
Defined Benefit Plan Disclosure
Plan assets	0	0
Other Postretirement  Benefits | Level 2 | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	0	0
Other Postretirement  Benefits | Level 2 | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	0	0
Other Postretirement  Benefits | Level 2 | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	0
Other Postretirement  Benefits | Level 2 | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	0	0
Other Postretirement  Benefits | Level 3
Defined Benefit Plan Disclosure
Plan assets	0	0
Other Postretirement  Benefits | Level 3 | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	0	0
Other Postretirement  Benefits | Level 3 | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	0	0
Other Postretirement  Benefits | Level 3 | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	0
Other Postretirement  Benefits | Level 3 | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	0	0
Other Postretirement  Benefits | Measured at NAV
Defined Benefit Plan Disclosure
Plan assets	55	42
Other Postretirement  Benefits | Measured at NAV | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	5	2
Other Postretirement  Benefits | Measured at NAV | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	2	3
Other Postretirement  Benefits | Measured at NAV | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	30
Other Postretirement  Benefits | Measured at NAV | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	$ 18	$ 37