Commitments, contingencies, and guarantees Commitments, contingencies, and guarantees (Collateral pledged under repurchase agreements) (Details) - USD ($) $ in Millions	Dec. 31, 2024		Dec. 31, 2023
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements	$ 2,731		$ 2,833
Securities Sold under Agreements to Repurchase	2,731		2,833
Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Deposits with U.S. regulatory authorities	2,890		2,924
Cash | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Deposits with U.S. regulatory authorities	21		34
Non-US [Member] | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Deposits with U.S. regulatory authorities	1,387		1,355
U.S. Treasury / Agency | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Deposits with U.S. regulatory authorities	104		105
Mortgage-backed securities | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Deposits with U.S. regulatory authorities	1,378		1,430
Repurchase Agreements [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Secured Borrowings, Gross, Difference, Amount	159	[1]	91
Maturity Less than 30 Days [Member] | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Deposits with U.S. regulatory authorities	1,387		1,355
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]
Deposits with U.S. regulatory authorities	0		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]
Deposits with U.S. regulatory authorities	1,387		1,355
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]
Deposits with U.S. regulatory authorities	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]
Deposits with U.S. regulatory authorities	0		0
Maturity 30 to 90 Days [Member] | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Deposits with U.S. regulatory authorities	473		1,051
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]
Deposits with U.S. regulatory authorities	19		33
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]
Deposits with U.S. regulatory authorities	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]
Deposits with U.S. regulatory authorities	0		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]
Deposits with U.S. regulatory authorities	454		913
Maturity Greater than 90 Days [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Deposits with U.S. regulatory authorities	1,030
Maturity Greater than 90 Days [Member] | Asset Pledged as Collateral without Right
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Deposits with U.S. regulatory authorities			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]
Deposits with U.S. regulatory authorities	2		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]
Deposits with U.S. regulatory authorities	0		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]
Deposits with U.S. regulatory authorities	104		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]
Deposits with U.S. regulatory authorities	$ 924		$ 517

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