Commitments, contingencies, and guarantees Commitments, Contingencies, And Guarantees (Collateral pledged under repurchase agreements) (Details) - USD ($) $ in Millions		Mar. 31, 2024	Dec. 31, 2023
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		$ 3,022	$ 2,833
Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		3,097	2,924
Cash [Member] | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		4	34
U.S. Treasury / Agency | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		100	105
Mortgage-backed securities | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		1,414	1,430
Repurchase Agreements [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Secured Borrowings, Gross, Difference, Amount	[1]	75	91
Non-US [Member] | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		1,579	1,355
Maturity Less than 30 Days [Member] | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		2,067	1,355
Maturity Less than 30 Days [Member] | Cash [Member] | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		0	0
Maturity Less than 30 Days [Member] | U.S. Treasury / Agency | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		0	0
Maturity Less than 30 Days [Member] | Mortgage-backed securities | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		488	0
Maturity Less than 30 Days [Member] | Non-US [Member] | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		1,579	1,355
Maturity 30 to 90 Days [Member] | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		1,030	1,051
Maturity 30 to 90 Days [Member] | Cash [Member] | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		4	33
Maturity 30 to 90 Days [Member] | U.S. Treasury / Agency | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		100	105
Maturity 30 to 90 Days [Member] | Mortgage-backed securities | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		926	913
Maturity 30 to 90 Days [Member] | Non-US [Member] | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		$ 0	0
Maturity Greater than 90 Days [Member] | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements			518
Maturity Greater than 90 Days [Member] | Cash [Member] | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements			1
Maturity Greater than 90 Days [Member] | U.S. Treasury / Agency | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements			0
Maturity Greater than 90 Days [Member] | Mortgage-backed securities | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements			517
Maturity Greater than 90 Days [Member] | Non-US [Member] | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements			$ 0

[1] Per the repurchase agreements, the amount of collateral posted is required to exceed the amount of gross liability.