Postretirement benefits (Narrative) (Details) - USD ($) $ in Millions		12 Months Ended
	Oct. 31, 2016	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Expenses recognized during period under the defined contributions plans		$ 283	$ 230	$ 214
Defined Benefit Plan, Plan Amendment [Abstract]
Other investments		5,527	1,341
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation		3,500	3,400
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		15
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		69	81	119
Actuarial Loss (gain)		2	(4)
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation		21	18
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		1
Defined Benefit Plan, Plan Amendment [Abstract]
(Increase) decrease in other comprehensive income, curtailment		0	0	0
Amortization of Prior Service Cost (Credit)		$ 0	0	26
Defined Benefit Plan, Equity Securities [Member] | Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage		55.00%
Defined Benefit Plan, Equity Securities [Member] | Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage		65.00%
Level 2 | Fixed Maturities [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		$ 34	50
Other Investments | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		35	31
UNITED STATES | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		3,589	3,316	4,151
Actuarial Loss (gain)		82	(890)
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation		45	66
Defined Benefit Plan, Plan Amendment [Abstract]
(Increase) decrease in other comprehensive income, curtailment		0	0	0
Amortization of Prior Service Cost (Credit)		0	0	0
Other investments		634	538
UNITED STATES | Postretirement Health Coverage [Member]
Defined Benefit Plan, Plan Amendment [Abstract]
Effect of Plan Amendment on Accumulated Benefit Obligation	$ 383
Amortization of Prior Service Cost (Credit)				26
UNITED STATES | Postretirement Health Coverage [Member] | Subject to Amortization [Member]
Defined Benefit Plan, Plan Amendment [Abstract]
Effect of Plan Amendment on Accumulated Benefit Obligation	$ 410
Non - U.S. | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		986	938	1,318
Actuarial Loss (gain)		29	(391)
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation		73	61
Defined Benefit Plan, Plan Amendment [Abstract]
(Increase) decrease in other comprehensive income, curtailment		0	0	0
Amortization of Prior Service Cost (Credit)		(1)	0	$ 0
Other investments		$ 227	$ 201