Fair value option - Changes in fair value under the fair value option (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	$ (66)	$ (280)	$ (170)	$ (709)
DVA
Changes in fair value under the fair value option election
Structured note credit adjustments	169	190	492	209
Federal funds sold and securities purchased under resale agreements
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	63	(114)	37	(58)
Federal funds sold and securities purchased under resale agreements | Principal transactions
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	63	(114)	37	(58)
Federal funds sold and securities purchased under resale agreements | All other income
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	0	0	0	0
Securities borrowed
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	(1)	(3)	(5)	(8)
Securities borrowed | Principal transactions
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	(1)	(3)	(5)	(8)
Securities borrowed | All other income
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	0	0	0	0
Debt and equity instruments, excluding loans
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	(144)	21	376	497
Debt and equity instruments, excluding loans | Principal transactions
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	(144)	20	375	495
Debt and equity instruments, excluding loans | All other income
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	0	1	1	2
Loans reported as trading assets: Changes in instrument-specific credit risk
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	17	150	241	916
Loans reported as trading assets: Changes in instrument-specific credit risk | Principal transactions
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	12	140	223	894
Loans reported as trading assets: Changes in instrument-specific credit risk | All other income
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	5	10	18	22
Loans reported as trading assets: Other changes in fair value
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	371	347	863	1,141
Loans reported as trading assets: Other changes in fair value | Principal transactions
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	94	98	206	200
Loans reported as trading assets: Other changes in fair value | All other income
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	277	249	657	941
Loans: Changes in instrument-specific credit risk
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	31	3	32	31
Loans: Changes in instrument-specific credit risk | Principal transactions
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	31	3	32	31
Loans: Changes in instrument-specific credit risk | All other income
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	0	0	0	0
Loans: Other changes in fair value
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	2	(2)	2	29
Loans: Other changes in fair value | Principal transactions
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	2	(2)	2	29
Loans: Other changes in fair value | All other income
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	0	0	0	0
Other assets
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	54	27	125	(103)
Other assets | Principal transactions
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	54	6	116	18
Other assets | All other income
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	0	21	9	(121)
Deposits
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	(112)	117	(75)	(94)
Deposits | Principal transactions
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	(112)	117	(75)	(94)
Deposits | All other income
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	0	0	0	0
Federal funds purchased and securities loaned or sold under repurchase agreements
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	(14)	15	(5)	(19)
Federal funds purchased and securities loaned or sold under repurchase agreements | Principal transactions
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	(14)	15	(5)	(19)
Federal funds purchased and securities loaned or sold under repurchase agreements | All other income
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	0	0	0	0
Other borrowed funds
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	2,015	(56)	2,121	(1,227)
Other borrowed funds | Principal transactions
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	2,015	(56)	2,121	(1,227)
Other borrowed funds | All other income
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	0	0	0	0
Trading liabilities
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	(6)	(2)	(20)	(11)
Trading liabilities | Principal transactions
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	(6)	(2)	(20)	(11)
Trading liabilities | All other income
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	0	0	0	0
Beneficial interests issued by consolidated VIEs
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	29	(54)	73	(191)
Beneficial interests issued by consolidated VIEs | Principal transactions
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	29	(54)	73	(191)
Beneficial interests issued by consolidated VIEs | All other income
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	0	0	0	0
Other liabilities
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	0	0	0	(27)
Other liabilities | Principal transactions
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	0	0	0	(27)
Other liabilities | All other income
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	0	0	0	0
Long-term debt: Changes in instrument-specific credit risk
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	299	162	624	167
Long-term debt: Changes in instrument-specific credit risk | Principal transactions
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	299	162	624	167
Long-term debt: Changes in instrument-specific credit risk | All other income
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	0	0	0	0
Long-term debt: Other changes in fair value
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	1,116	170	1,466	(621)
Long-term debt: Other changes in fair value | Principal transactions
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	1,116	170	1,466	(621)
Long-term debt: Other changes in fair value | All other income
Changes in fair value under the fair value option election
Fair value option, changes in fair value gain (loss)	$ 0	$ 0	$ 0	$ 0