Commitments, contingencies, and guarantees Commitments, contingencies, and guarantees (Collateral pledged under repurchase agreements) (Details) - USD ($) $ in Millions		Dec. 31, 2023	Dec. 31, 2022
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements (includes VIE balances of $1,009 and nil)		$ 2,833	$ 1,419
Securities Sold under Agreements to Repurchase		2,833	1,419
Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		2,924	1,527
Cash | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		34	12
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		1,355	0
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		105	101
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		1,430	1,414
Repurchase Agreements [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Secured Borrowings, Gross, Difference, Amount	[1]	91	108
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		1,355	933
Maturity Less than 30 Days [Member] | Cash | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		0	12
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		1,355	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		0	921
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		1,051	594
Maturity 30 to 90 Days [Member] | Cash | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Assets pledged under repurchase agreements		33	0
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 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		105	101
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		913	$ 493
Maturity Greater than 90 Days [Member]
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 | 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] | 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
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

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