Income taxes - Uncertain tax positions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance, January 1	$ 69	$ 89	$ 303
Additions based on tax positions related to the current year	3	2	3
Additions for tax positions of prior years	10	7	35
Reductions for tax positions of prior years	0	(6)	(249)
Settlements with tax authorities	0	(23)	0
Expiration of the statute of limitations for assessing taxes	0	0	(3)
Balance, December 31	82	69	89
Interest income (expense) recognized in the year ended December 31	(1)	(5)	39
Interest payable as of December 31	$ 3	$ 13	$ 8