Postretirement benefits Components of net periodic benefit costs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	$ 1	$ 1
Non-service (benefit) cost	(55)	(51)
Net periodic benefit cost (benefit)	(54)	(50)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	0	0
Interest cost	0	0
Expected return on plan assets	0	0
Defined Benefit Plan, Amortization of Gain (Loss)	0	0
Amortization of prior service cost	0	(20)
Settlements	0	0
Non-service (benefit) cost	0	(20)
Net periodic benefit cost (benefit)	0	(20)
Losses and loss expenses | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	0	0
Non-service (benefit) cost	(5)	(5)
Losses and loss expenses | Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	0	0
Non-service (benefit) cost	0	(2)
Administrative Expense | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	1	1
Non-service (benefit) cost	(50)	(46)
Administrative Expense | Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	0	0
Non-service (benefit) cost	0	(18)
Foreign Plan [Member] | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	1	1
Interest cost	6	5
Expected return on plan assets	(11)	(11)
Defined Benefit Plan, Amortization of Gain (Loss)	0	1
Amortization of prior service cost	0	0
Settlements	0	0
Non-service (benefit) cost	(5)	(5)
Net periodic benefit cost (benefit)	(4)	(4)
UNITED STATES | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	0	0
Interest cost	21	18
Expected return on plan assets	(71)	(64)
Defined Benefit Plan, Amortization of Gain (Loss)	0	0
Amortization of prior service cost	0	0
Settlements	0	0
Non-service (benefit) cost	(50)	(46)
Net periodic benefit cost (benefit)	$ (50)	$ (46)