Fair Value Disclosures - Changes in Level 3 Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value, beginning balance	$ 457	$ 416	$ 337	$ 300
Realized and Unrealized Gains (Losses),Assets	6	(20)	3	3
Purchases, Assets	4	119	475	246
Sales and Maturities, Assets	(88)	(2)	(442)	(40)
Issuances and other Settlements, Assets	0	0	0	0
Transfers into Level 3, Assets	2	23	11	33
Transfers out of Level 3, Assets	(4)	(8)	(7)	(14)
Assets measured at fair value, ending balance	377	528	377	528
Total Net Unrealized Gains (Losses) Included in Earnings	6	(20)	3	3
Other Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value, beginning balance	150	109	120	0
Assets measured at fair value, ending balance	157	107	157	107
Other Liabilities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities measured at fair value, beginning balance	298	254	279	280
Liabilities measured at fair value, ending balance	279	295	279	295
Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value, beginning balance	307	307	217	300
Realized and Unrealized Gains (Losses),Assets	(1)	(18)	3	5
Purchases, Assets	4	119	438	137
Sales and Maturities, Assets	(88)	(2)	(442)	(40)
Issuances and other Settlements, Assets	0	0	0	0
Transfers into Level 3, Assets	2	23	11	33
Transfers out of Level 3, Assets	(4)	(8)	(7)	(14)
Assets measured at fair value, ending balance	220	421	220	421
Total Net Unrealized Gains (Losses) Included in Earnings	(1)	(18)	3	5
Debt securities [Member] | Trading [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value, beginning balance	82	41	42	52
Realized and Unrealized Gains (Losses),Assets	(2)	(1)	2	(1)
Purchases, Assets	0	2	36	8
Sales and Maturities, Assets	(1)	(2)	(1)	(19)
Issuances and other Settlements, Assets	0	0	0	0
Transfers into Level 3, Assets	0	0	0	0
Transfers out of Level 3, Assets	0	0	0	0
Assets measured at fair value, ending balance	79	40	79	40
Total Net Unrealized Gains (Losses) Included in Earnings	$ (2)	$ (1)	$ 2	$ (1)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Nonoperating Income (Expense)	Nonoperating Income (Expense)	Nonoperating Income (Expense)	Nonoperating Income (Expense)
Consolidated Variable Interest Entities [Member] | Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value, beginning balance	$ 225	$ 266	$ 175	$ 248
Realized and Unrealized Gains (Losses),Assets	1	(17)	1	6
Purchases, Assets	4	117	402	129
Sales and Maturities, Assets	(87)	0	(441)	(21)
Issuances and other Settlements, Assets	0	0	0	0
Transfers into Level 3, Assets	2	23	11	33
Transfers out of Level 3, Assets	(4)	(8)	(7)	(14)
Assets measured at fair value, ending balance	141	381	141	381
Total Net Unrealized Gains (Losses) Included in Earnings	1	(17)	1	6
Other Assets One [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Realized and Unrealized Gains (Losses),Assets	7	(2)	0	(2)
Purchases, Assets	0	0	37	109
Sales and Maturities, Assets	0	0	0	0
Issuances and other Settlements, Assets	0	0	0	0
Transfers into Level 3, Assets	0	0	0	0
Transfers out of Level 3, Assets	0	0	0	0
Total Net Unrealized Gains (Losses) Included in Earnings	7	(2)	0	(2)
Other Liabilities One [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Realized and Unrealized Gains (Losses), Liabilities	16	3	19	7
Purchases, Liabilities	0	0	0	0
Sales and Maturities, Liabilities	0	0	0	0
Issuances and other Settlements, Liabilities	(3)	44	19	22
Transfers into Level 3, Liabilities	0	0	0	0
Transfers out of Level 3, Liabilities	0	0	0	0
Total Net Unrealized Gains (Losses) Included in Earnings	$ 16	$ 3	$ 19	$ 7
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Nonoperating Income (Expense)	Nonoperating Income (Expense)	Nonoperating Income (Expense)	Nonoperating Income (Expense)