Fair Value Option - Changes in Fair Value Under the Fair Value Option (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Federal funds sold and securities purchased under resale agreements
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	$ (2)	$ (299)	$ (14)	$ 244
Federal funds sold and securities purchased under resale agreements | Principal transactions
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(2)	(299)	(14)	244
Federal funds sold and securities purchased under resale agreements | All other income
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	0	0	0
Securities borrowed
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(27)	(58)	(97)	168
Securities borrowed | Principal transactions
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(27)	(58)	(97)	168
Securities borrowed | All other income
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	0	0	0
Debt and equity instruments, excluding loans
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	366	1,209	987	(1,230)
Debt and equity instruments, excluding loans | Principal transactions
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	367	1,209	988	(1,229)
Debt and equity instruments, excluding loans | All other income
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(1)	0	(1)	(1)
Loans reported as trading assets: Changes in instrument-specific credit risk
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	72	401	276	(255)
Loans reported as trading assets: Changes in instrument-specific credit risk | Principal transactions
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	72	401	276	(255)
Loans reported as trading assets: Changes in instrument-specific credit risk | All other income
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	0	0	0
Loans reported as trading assets: Other changes in fair value
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(7)	0	(8)	1
Loans reported as trading assets: Other changes in fair value | Principal transactions
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(7)	0	(8)	1
Loans reported as trading assets: Other changes in fair value | All other income
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	0	0	0
Loans: Changes in instrument-specific credit risk
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	181	5	419	46
Loans: Changes in instrument-specific credit risk | Principal transactions
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	184	(33)	421	31
Loans: Changes in instrument-specific credit risk | All other income
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(3)	38	(2)	15
Loans: Other changes in fair value
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	927	750	1,017	1,759
Loans: Other changes in fair value | Principal transactions
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	143	(4)	(107)	264
Loans: Other changes in fair value | All other income
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	784	754	1,124	1,495
Other assets
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	5	42	5	110
Other assets | Principal transactions
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	9	17	28	102
Other assets | All other income
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(4)	25	(23)	8
Deposits
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(258)	(362)	(91)	(465)
Deposits | Principal transactions
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(258)	(362)	(91)	(465)
Realized gains/(losses) due to instrument-specific credit risk recorded in principal transactions revenue	0	21	(2)	19
Deposits | All other income
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	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
Total nonrecurring fair value gains/(losses)	(3)	181	31	(78)
Federal funds purchased and securities loaned or sold under repurchase agreements | Principal transactions
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(3)	181	31	(78)
Federal funds purchased and securities loaned or sold under repurchase agreements | All other income
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	0	0	0
Short-term borrowings
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(489)	(631)	(611)	1,089
Short-term borrowings | Principal transactions
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(489)	(631)	(611)	1,089
Short-term borrowings | All other income
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	0	0	0
Trading liabilities
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(1)	0	(1)	0
Trading liabilities | Principal transactions
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(1)	0	(1)	0
Trading liabilities | All other income
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	0	0	0
Other liabilities
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	1	(11)	2	(46)
Other liabilities | Principal transactions
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	1	(11)	2	(46)
Other liabilities | All other income
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	0	0	0
Long-term debt
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(2,152)	(3,583)	(910)	603
Long-term debt | Principal transactions
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(2,152)	(3,581)	(905)	600
Long-term debt | All other income
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	$ 0	$ (2)	$ (5)	$ 3