Variable interest entities and securitization - Assets and Liabilities of VIEs (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Trading assets	$ 17,854	$ 15,272
Other assets	1,313	1,009
Other liabilities	433	1,110
Nonredeemable noncontrolling interests	273	143
VME classification of carrying amount, assets	185	314
VME classification of carrying amount, liabilities	1	3
Noncontrolling interest in VME	48	76
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Trading assets	887	882
Other assets	18	5
Total assets	905	887
Other liabilities	405	403
Total liabilities	405	403
Nonredeemable noncontrolling interests	273	143
Investment Management funds | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Trading assets	487	482
Other assets	18	5
Total assets	505	487
Other liabilities	5	3
Total liabilities	5	3
Nonredeemable noncontrolling interests	273	143
Securitization | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Trading assets	400	400
Other assets	0	0
Total assets	400	400
Other liabilities	400	400
Total liabilities	400	400
Nonredeemable noncontrolling interests	$ 0	$ 0