Employee benefit plans - Components of net periodic benefit cost (Details) - Pension - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Employee benefit plans
Interest cost	$ 4	$ 3
Expected return on plan assets	(7)	(7)
Amortization of net loss		1
Expenses paid	1	1
Net periodic benefit credit	$ (2)	$ (2)