Postemployment benefit plans - Fair value of pension and other postretirement benefit plan assets, by category (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Pension Plan | U.S. Pension Benefits
Defined Benefit Plan Disclosure
Plan assets	$ 11,898	$ 12,738	$ 12,456
Pension Plan | U.S. Pension Benefits | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	1,177	1,222
Pension Plan | U.S. Pension Benefits | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	956	913
Pension Plan | U.S. Pension Benefits | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	5,465	5,772
Pension Plan | U.S. Pension Benefits | Non-U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	972	1,228
Pension Plan | U.S. Pension Benefits | U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	2,656	2,988
Pension Plan | U.S. Pension Benefits | U.S. governmental agency
Defined Benefit Plan Disclosure
Plan assets	180	84
Pension Plan | U.S. Pension Benefits | Non-U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	132	100
Pension Plan | U.S. Pension Benefits | Real estate
Defined Benefit Plan Disclosure
Plan assets		3
Pension Plan | U.S. Pension Benefits | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	360	428
Pension Plan | U.S. Pension Benefits | Level 1
Defined Benefit Plan Disclosure
Plan assets	2,081	2,116
Pension Plan | U.S. Pension Benefits | Level 1 | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	1,087	1,107
Pension Plan | U.S. Pension Benefits | Level 1 | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	946	910
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
Pension Plan | U.S. Pension Benefits | Level 1 | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	48	99
Pension Plan | U.S. Pension Benefits | Level 2
Defined Benefit Plan Disclosure
Plan assets	9,348	10,149
Pension Plan | U.S. Pension Benefits | Level 2 | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	0	10
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	5,396	5,706
Pension Plan | U.S. Pension Benefits | Level 2 | Non-U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	972	1,228
Pension Plan | U.S. Pension Benefits | Level 2 | U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	2,656	2,988
Pension Plan | U.S. Pension Benefits | Level 2 | U.S. governmental agency
Defined Benefit Plan Disclosure
Plan assets	180	84
Pension Plan | U.S. Pension Benefits | Level 2 | Non-U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	132	100
Pension Plan | U.S. Pension Benefits | Level 2 | Real estate
Defined Benefit Plan Disclosure
Plan assets		0
Pension Plan | U.S. Pension Benefits | Level 2 | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	12	33
Pension Plan | U.S. Pension Benefits | Level 3
Defined Benefit Plan Disclosure
Plan assets	71	63
Pension Plan | U.S. Pension Benefits | Level 3 | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	28	24
Pension Plan | U.S. Pension Benefits | Level 3 | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	10	3
Pension Plan | U.S. Pension Benefits | Level 3 | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	33	33
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
Pension Plan | U.S. Pension Benefits | Level 3 | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | U.S. Pension Benefits | Measured at NAV
Defined Benefit Plan Disclosure
Plan assets	398	410
Pension Plan | U.S. Pension Benefits | Measured at NAV | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	62	81
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	36	33
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
Pension Plan | U.S. Pension Benefits | Measured at NAV | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	300	296
Pension Plan | Non-U.S.  Pension Benefits
Defined Benefit Plan Disclosure
Plan assets	3,203	3,467	3,244
Pension Plan | Non-U.S.  Pension Benefits | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	74	73
Pension Plan | Non-U.S.  Pension Benefits | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	243	282
Pension Plan | Non-U.S.  Pension Benefits | Global equities
Defined Benefit Plan Disclosure
Plan assets	49	48
Pension Plan | Non-U.S.  Pension Benefits | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	87	91
Pension Plan | Non-U.S.  Pension Benefits | Non-U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	468	466
Pension Plan | Non-U.S.  Pension Benefits | U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	61	63
Pension Plan | Non-U.S.  Pension Benefits | Non-U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	916	998
Pension Plan | Non-U.S.  Pension Benefits | Global fixed income
Defined Benefit Plan Disclosure
Plan assets	297	307
Pension Plan | Non-U.S.  Pension Benefits | Real estate
Defined Benefit Plan Disclosure
Plan assets	216	219
Pension Plan | Non-U.S.  Pension Benefits | Insurance contracts
Defined Benefit Plan Disclosure
Plan assets	601	675
Pension Plan | Non-U.S.  Pension Benefits | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	191	245
Pension Plan | Non-U.S.  Pension Benefits | Level 1
Defined Benefit Plan Disclosure
Plan assets	338	383
Pension Plan | Non-U.S.  Pension Benefits | Level 1 | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	74	73
Pension Plan | Non-U.S.  Pension Benefits | Level 1 | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	197	228
Pension Plan | Non-U.S.  Pension Benefits | Level 1 | Global equities
Defined Benefit Plan Disclosure
Plan assets	32	28
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	0
Pension Plan | Non-U.S.  Pension Benefits | Level 1 | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	35	54
Pension Plan | Non-U.S.  Pension Benefits | Level 2
Defined Benefit Plan Disclosure
Plan assets	2,025	2,143
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	26	33
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | Global equities
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	87	91
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | Non-U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	468	466
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	61	63
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | Non-U.S. government bonds
Defined Benefit Plan Disclosure
Plan assets	916	998
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | Global fixed income
Defined Benefit Plan Disclosure
Plan assets	104	91
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | Real estate
Defined Benefit Plan Disclosure
Plan assets	207	210
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | Insurance contracts
Defined Benefit Plan Disclosure
Plan assets	0	0
Pension Plan | Non-U.S.  Pension Benefits | Level 2 | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	156	191
Pension Plan | Non-U.S.  Pension Benefits | Level 3
Defined Benefit Plan Disclosure
Plan assets	601	675
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	601	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	239	266
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	20	21
Pension Plan | Non-U.S.  Pension Benefits | Measured at NAV | Global equities
Defined Benefit Plan Disclosure
Plan assets	17	20
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	193	216
Pension Plan | Non-U.S.  Pension Benefits | Measured at NAV | Real estate
Defined Benefit Plan Disclosure
Plan assets	9	9
Pension Plan | Non-U.S.  Pension Benefits | Measured at NAV | Insurance contracts
Defined Benefit Plan Disclosure
Plan assets	0	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	88	144	$ 102
Other Postretirement  Benefits | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	43	70
Other Postretirement  Benefits | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	20	25
Other Postretirement  Benefits | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	20	30
Other Postretirement  Benefits | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	5	19
Other Postretirement  Benefits | Level 1
Defined Benefit Plan Disclosure
Plan assets	59	89
Other Postretirement  Benefits | Level 1 | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	41	65
Other Postretirement  Benefits | Level 1 | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	18	23
Other Postretirement  Benefits | Level 1 | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	0	0
Other Postretirement  Benefits | Level 1 | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	0	1
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	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	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	29	55
Other Postretirement  Benefits | Measured at NAV | U.S. equities
Defined Benefit Plan Disclosure
Plan assets	2	5
Other Postretirement  Benefits | Measured at NAV | Non-U.S. equities
Defined Benefit Plan Disclosure
Plan assets	2	2
Other Postretirement  Benefits | Measured at NAV | U.S. corporate bonds
Defined Benefit Plan Disclosure
Plan assets	20	30
Other Postretirement  Benefits | Measured at NAV | Cash, short-term instruments and other
Defined Benefit Plan Disclosure
Plan assets	$ 5	$ 18