Employee benefit plans (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Health care benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 0	$ 0	$ 0	$ 0
Interest cost	1	1	2	3	4
Expected return on assets	(2)	(1)	(2)	(5)	(5)
Other	0	0	(1)	0	(2)
Net periodic benefit (credit) cost	(1)	0	(1)	(2)	(3)
Domestic | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	0	0	0
Interest cost	35	34	39	103	117
Expected return on assets	(75)	(75)	(80)	(225)	(239)
Other	24	24	22	73	65
Net periodic benefit (credit) cost	(16)	(17)	(19)	(49)	(57)
Foreign | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	4	3	3	11	9
Interest cost	6	7	7	19	20
Expected return on assets	(9)	(8)	(10)	(26)	(29)
Other	3	3	2	10	8
Net periodic benefit (credit) cost	$ 4	$ 5	$ 2	$ 14	$ 8