Fair Values - Activity of Level 3 Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Recurring - Level 3 - USD ($) $ in Millions	3 Months Ended					12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Liabilities at Fair Value
Portion of unrealized losses (gains) recorded in OCI—Change in net DVA						$ (17)	$ 63	$ 182
Deposits
Liabilities at Fair Value
Beginning balance			$ 126		$ 179	126	179	27
Realized and unrealized losses (gains)						0	15	20
Issuances						0	21	101
Settlements						(10)	(17)	(15)
Net transfers						(49)	(72)	46
Ending balance						67	126	179
Unrealized losses (gains)						0	15	20
Nonderivative trading liabilities
Liabilities at Fair Value
Beginning balance			79		37	79	37	16
Realized and unrealized losses (gains)						(21)	(18)	(21)
Purchases						(30)	(35)	(65)
Sales						43	27	38
Settlements						0	3	0
Net transfers						(10)	65	69
Ending balance						61	79	37
Unrealized losses (gains)						(21)	(18)	(21)
Securities sold under agreements to repurchase
Liabilities at Fair Value
Beginning balance			444		0	444	0	0
Realized and unrealized losses (gains)						1	(27)	0
Issuances						0	470	0
Net transfers						206	1	0
Ending balance						651	444	0
Unrealized losses (gains)						1	(27)	0
Other secured financings
Liabilities at Fair Value
Beginning balance			516		109	516	109	208
Realized and unrealized losses (gains)						(17)	21	5
Issuances						449	208	0
Settlements						(518)	(217)	(8)
Net transfers						(27)	395	(96)
Ending balance						403	516	109
Unrealized losses (gains)						(16)	21	5
Borrowings
Liabilities at Fair Value
Beginning balance			4,374		4,088	4,374	4,088	3,806
Realized and unrealized losses (gains)						(99)	204	728
Issuances						717	980	1,181
Settlements						(448)	(461)	(950)
Net transfers						(2,387)	(437)	(677)
Ending balance						2,157	4,374	4,088
Unrealized losses (gains)						(114)	201	600
Transfers from Level 3 to Level 2		$ 2,200
Interest rate
Assets at Fair value
Beginning balance			682		777	682	777	618
Realized and unrealized gains (losses)						284	(150)	17
Purchases						67	174	98
Issuances						(52)	(44)	(16)
Settlements						14	40	1
Net transfers						(287)	(115)	59
Ending balance						708	682	777
Unrealized gains (losses)						292	(34)	87
Credit
Assets at Fair value
Beginning balance			49		124	49	124	40
Realized and unrealized gains (losses)						95	(91)	(24)
Purchases						18	98	144
Issuances						(46)	(112)	(190)
Settlements						58	94	111
Net transfers						(76)	(64)	43
Ending balance						98	49	124
Unrealized gains (losses)						122	(111)	(17)
Foreign exchange
Assets at Fair value
Beginning balance			61		(31)	61	(31)	75
Realized and unrealized gains (losses)						(89)	156	(295)
Purchases						2	4	2
Issuances						(15)	0	0
Settlements						16	(17)	7
Net transfers						77	(51)	180
Ending balance						52	61	(31)
Unrealized gains (losses)						(62)	94	(187)
Equity
Assets at Fair value
Beginning balance			(2,231)		(1,684)	(2,231)	(1,684)	(1,485)
Realized and unrealized gains (losses)						344	72	(260)
Purchases						70	179	155
Issuances						(443)	(713)	(643)
Settlements						160	(354)	242
Net transfers						1,155	269	307
Ending balance						(945)	(2,231)	(1,684)
Unrealized gains (losses)						(103)	(210)	(194)
Liabilities at Fair Value
Transfers from Level 3 to Level 2		1,000
Commodity and other
Assets at Fair value
Beginning balance			1,709		1,612	1,709	1,612	2,052
Realized and unrealized gains (losses)						529	251	73
Purchases						44	89	152
Issuances						(86)	(57)	(92)
Settlements						(599)	(183)	(611)
Net transfers						(68)	(3)	38
Ending balance						1,529	1,709	1,612
Unrealized gains (losses)						141	(309)	(113)
U.S. Treasury and agency securities
Assets at Fair value
Beginning balance			9		22	9	22	54
Realized and unrealized gains (losses)						0	1	4
Purchases						2	0	17
Sales						(9)	(22)	(54)
Net transfers						0	8	1
Ending balance						2	9	22
Unrealized gains (losses)						0	0	4
Other sovereign government obligations
Assets at Fair value
Beginning balance			268		5	268	5	17
Realized and unrealized gains (losses)						(1)	0	(3)
Purchases						146	265	7
Sales						(192)	(2)	(6)
Net transfers						(10)	0	(10)
Ending balance						211	268	5
Unrealized gains (losses)						0	0	(3)
State and municipal securities
Assets at Fair value
Beginning balance			0		1	0	1	148
Purchases						4	0	0
Sales						(4)	0	(147)
Net transfers						13	(1)	0
Ending balance						13	0	1
Unrealized gains (losses)						0	0	0
MABS
Assets at Fair value
Beginning balance			322		438	322	438	354
Realized and unrealized gains (losses)						51	(66)	(16)
Purchases						254	175	132
Sales						(215)	(244)	(175)
Settlements						0	0	(44)
Net transfers						(68)	19	187
Ending balance						344	322	438
Unrealized gains (losses)						(10)	(49)	(57)
Loans and lending commitments
Assets at Fair value
Beginning balance			5,759		5,073	5,759	5,073	6,870
Realized and unrealized gains (losses)						51	(65)	38
Purchases						2,446	3,479	2,337
Sales						(2,609)	(957)	(1,268)
Settlements						(1,268)	(2,196)	(2,291)
Net transfers						(573)	425	(613)
Ending balance						3,806	5,759	5,073
Unrealized gains (losses)						(7)	58	(9)
Liabilities at Fair Value
Transfers from Level 3 to Level 2	$ 895			$ 707
Transfers of equity margin loans from Level 2 into Level 3					857
Corporate and other debt
Assets at Fair value
Beginning balance			3,435		1,396	3,435	1,396	1,076
Realized and unrealized gains (losses)						(140)	318	418
Purchases						1,355	2,623	650
Sales						(785)	(617)	(729)
Settlements						0	(311)	(7)
Net transfers						(1,892)	26	(12)
Ending balance						1,973	3,435	1,396
Unrealized gains (losses)						(25)	311	361
Liabilities at Fair Value
Transfers from Level 3 to Level 2		$ 2,000
Corporate equities
Assets at Fair value
Beginning balance			86		97	86	97	95
Realized and unrealized gains (losses)						(8)	(55)	(8)
Purchases						121	36	32
Sales						(50)	(17)	(271)
Net transfers						(34)	25	249
Ending balance						115	86	97
Unrealized gains (losses)						(3)	(39)	1
Investments
Assets at Fair value
Beginning balance			828		858	828	858	757
Realized and unrealized gains (losses)						382	32	78
Purchases						226	61	40
Sales						(115)	(106)	(41)
Net transfers						(196)	(17)	24
Ending balance						1,125	828	858
Unrealized gains (losses)						359	(45)	67
Investment securities—AFS
Assets at Fair value
Beginning balance			2,804		0	2,804	0	0
Realized and unrealized gains (losses)						(4)	5	0
Purchases						0	2,799	0
Sales						(203)	0	0
Net transfers						(2,597)	0	0
Ending balance						0	2,804	0
Unrealized gains (losses)						0	5	0
Liabilities at Fair Value
Transfers from Level 3 to Level 2			2,500
Securities purchased under agreements to resell
Assets at Fair value
Beginning balance			$ 3		$ 0	3	0	0
Net transfers						(3)	3	0
Ending balance						0	3	0
Unrealized gains (losses)						$ 0	$ 0	$ 0