Fair Value Option - Changes in Fair Value Under the Fair Value Option (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
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)	$ (76)	$ 94	$ (143)	$ 167
Federal funds sold and securities purchased under resale agreements \| Income Statement Location [Axis]: us-gaap:NoninterestIncomeOther
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	0	0	0
Federal funds sold and securities purchased under resale agreements \| Income Statement Location [Axis]: us-gaap:PrincipalTransactionsRevenue
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(76)	94	(143)	167
Securities borrowed
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(7)	(2)	(9)	(6)
Securities borrowed \| Income Statement Location [Axis]: us-gaap:NoninterestIncomeOther
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	0	0	0
Securities borrowed \| Income Statement Location [Axis]: us-gaap:PrincipalTransactionsRevenue
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(7)	(2)	(9)	(6)
Debt and equity instruments, excluding loans
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	1,562	1,055	2,337	2,103
Debt and equity instruments, excluding loans \| Income Statement Location [Axis]: us-gaap:NoninterestIncomeOther
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 \| Income Statement Location [Axis]: us-gaap:PrincipalTransactionsRevenue
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	1,562	1,055	2,337	2,103
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)	(70)	111	209	134
Loans reported as trading assets: Changes in instrument-specific credit risk \| Income Statement Location [Axis]: us-gaap:NoninterestIncomeOther
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: Changes in instrument-specific credit risk \| Income Statement Location [Axis]: us-gaap:PrincipalTransactionsRevenue
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(70)	111	209	134
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)	(3)	6	12	31
Loans reported as trading assets: Other changes in fair value \| Income Statement Location [Axis]: us-gaap:NoninterestIncomeOther
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	6	8	14
Loans reported as trading assets: Other changes in fair value \| Income Statement Location [Axis]: us-gaap:PrincipalTransactionsRevenue
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(3)	0	4	17
Loans: Changes in instrument-specific credit risk
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	37	60	334	477
Loans: Changes in instrument-specific credit risk \| Income Statement Location [Axis]: us-gaap:NoninterestIncomeOther
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(8)	0	(7)	0
Loans: Changes in instrument-specific credit risk \| Income Statement Location [Axis]: us-gaap:PrincipalTransactionsRevenue
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	45	60	341	477
Loans: Other changes in fair value
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(858)	338	(736)	922
Loans: Other changes in fair value \| Income Statement Location [Axis]: us-gaap:NoninterestIncomeOther
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(627)	230	(463)	557
Loans: Other changes in fair value \| Income Statement Location [Axis]: us-gaap:PrincipalTransactionsRevenue
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(231)	108	(273)	365
Other assets
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	20	23	51
Other assets \| Income Statement Location [Axis]: us-gaap:NoninterestIncomeOther
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	(4)	(2)	(4)
Other assets \| Income Statement Location [Axis]: us-gaap:PrincipalTransactionsRevenue
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	24	25	55
Deposits
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	110	(567)	(135)	(1,559)
Deposits \| Income Statement Location [Axis]: us-gaap:NoninterestIncomeOther
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	0	0	0
Deposits \| Income Statement Location [Axis]: us-gaap:PrincipalTransactionsRevenue
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	110	(567)	(135)	(1,559)
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)	61	(13)	97	(25)
Federal funds purchased and securities loaned or sold under repurchase agreements \| Income Statement Location [Axis]: us-gaap:NoninterestIncomeOther
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 \| Income Statement Location [Axis]: us-gaap:PrincipalTransactionsRevenue
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	61	(13)	97	(25)
Short-term borrowings
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(534)	(685)	(1,216)	(1,224)
Short-term borrowings \| Income Statement Location [Axis]: us-gaap:NoninterestIncomeOther
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	0	0	0
Short-term borrowings \| Income Statement Location [Axis]: us-gaap:PrincipalTransactionsRevenue
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(534)	(685)	(1,216)	(1,224)
Trading liabilities
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(30)	(1)	7	19
Trading liabilities \| Income Statement Location [Axis]: us-gaap:NoninterestIncomeOther
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	0	0	0
Trading liabilities \| Income Statement Location [Axis]: us-gaap:PrincipalTransactionsRevenue
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(30)	(1)	7	19
Beneficial interests issued by consolidated VIEs
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	0	0	0
Beneficial interests issued by consolidated VIEs \| Income Statement Location [Axis]: us-gaap:NoninterestIncomeOther
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	0	0	0
Beneficial interests issued by consolidated VIEs \| Income Statement Location [Axis]: us-gaap:PrincipalTransactionsRevenue
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)	(7)	3	(9)	(2)
Other liabilities \| Income Statement Location [Axis]: us-gaap:NoninterestIncomeOther
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	0	0	0	0
Other liabilities \| Income Statement Location [Axis]: us-gaap:PrincipalTransactionsRevenue
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	(7)	3	(9)	(2)
Long-term debt
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	3,700	(2,901)	(622)	(6,262)
Long-term debt \| Income Statement Location [Axis]: us-gaap:NoninterestIncomeOther
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	3	(1)	(1)	(5)
Long-term debt \| Income Statement Location [Axis]: us-gaap:PrincipalTransactionsRevenue
Changes in fair value under the fair value option election
Total nonrecurring fair value gains/(losses)	$ 3,697	$ (2,900)	$ (621)	$ (6,257)