Fair Value Measurements - Changes in Fair Value of Level 3 Assets and Liabilities (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net income	Net income
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net income	Net income
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net income	Net income
Derivatives liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total liabilities, ending balance	$ (196)	$ (223)
Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total assets, beginning balance	138	(83)
Assets, Total Realized/Unrealized Gains (Losses) Included in Earnings	54	126
Assets, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss)	(1)	1
Assets, Purchases	17	1
Assets, Issuances	0	0
Assets, Settlements	(16)	21
Assets, Transfers Into Level 3	(2)	0
Assets Transfers out of Level 3	(10)	2
Total assets, ending balance	180	68
Assets, Current Period Unrealized Gains (Losses) Still Held Included in Earnings	50	112
Assets, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income (Loss)	(1)	1
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total liabilities, beginning balance	(2,212)	(3,012)
Total Realized/Unrealized Gains (Losses) Included in Earnings	(111)	(172)
Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	(4)	26
Purchases	0	0
Issuances	(401)	(189)
Settlements	316	255
Transfers Into Level 3	(13)	(1)
Transfers Out of Level 3	135	428
Total liabilities, ending balance	(2,290)	(2,665)
Current Period Unrealized Gains (Losses) Still Held Included in Earnings	(72)	(121)
Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income (Loss)	(4)	26
Level 3 | Interest rate contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	(4)	(5)
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Earnings	(1)	1
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	0	0
Derivatives, net, Purchases	0	0
Derivatives, net, Issuances	0	0
Derivatives, net, Settlements	0	0
Derivatives, net, Transfers into Level 3	2	0
Derivatives, net, Transfers out of Level 3	0	0
Derivatives, net, Ending Balance	(3)	(4)
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Earnings	(1)	1
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income (Loss)	0	0
Level 3 | Foreign exchange contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	0	0
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Earnings	0	0
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	0	0
Derivatives, net, Purchases	0	0
Derivatives, net, Issuances	0	0
Derivatives, net, Settlements	0	0
Derivatives, net, Transfers into Level 3	0	0
Derivatives, net, Transfers out of Level 3	0	0
Derivatives, net, Ending Balance	0	0
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Earnings	0	0
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income (Loss)	0	0
Level 3 | Equity contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	21	(226)
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Earnings	59	128
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	0	0
Derivatives, net, Purchases	0	0
Derivatives, net, Issuances	0	0
Derivatives, net, Settlements	3	12
Derivatives, net, Transfers into Level 3	(7)	0
Derivatives, net, Transfers out of Level 3	(9)	2
Derivatives, net, Ending Balance	67	(84)
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Earnings	50	112
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income (Loss)	0	0
Level 3 | Credit contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	1	2
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Earnings	(3)	0
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	0	0
Derivatives, net, Purchases	0	0
Derivatives, net, Issuances	0	0
Derivatives, net, Settlements	(1)	0
Derivatives, net, Transfers into Level 3	0	0
Derivatives, net, Transfers out of Level 3	3	0
Derivatives, net, Ending Balance	0	2
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Earnings	0	0
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income (Loss)	0	0
Level 3 | Other Contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	(35)	(33)
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Earnings	(2)	(2)
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	0	0
Derivatives, net, Purchases	0	0
Derivatives, net, Issuances	0	0
Derivatives, net, Settlements	7	11
Derivatives, net, Transfers into Level 3	0	0
Derivatives, net, Transfers out of Level 3	0	0
Derivatives, net, Ending Balance	(30)	(24)
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Earnings	0	0
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income (Loss)	$ 0	$ 0
Asset-backed securities available-for-sale
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other comprehensive income (loss), net of tax	Other comprehensive income (loss), net of tax
Asset-backed securities available-for-sale | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total assets, beginning balance	$ 104	$ 108
Assets, Total Realized/Unrealized Gains (Losses) Included in Earnings	0	0
Assets, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss)	(1)	1
Assets, Purchases	0	0
Assets, Issuances	0	0
Assets, Settlements	(1)	(2)
Assets, Transfers Into Level 3	0	0
Assets Transfers out of Level 3	0	0
Total assets, ending balance	102	107
Assets, Current Period Unrealized Gains (Losses) Still Held Included in Earnings	0	0
Assets, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income (Loss)	$ (1)	$ 1
Mortgage servicing rights
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (loss)	Other income (loss)
Mortgage servicing rights | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total assets, beginning balance	$ 19	$ 22
Assets, Total Realized/Unrealized Gains (Losses) Included in Earnings	0	(1)
Assets, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss)	0	0
Assets, Purchases	0	0
Assets, Issuances	0	0
Assets, Settlements	0	0
Assets, Transfers Into Level 3	0	0
Assets Transfers out of Level 3	0	0
Total assets, ending balance	19	21
Assets, Current Period Unrealized Gains (Losses) Still Held Included in Earnings	0	(1)
Assets, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income (Loss)	0	0
Derivative assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total assets, ending balance	230	113
Domestic deposits | Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total liabilities, beginning balance	(293)	(373)
Total Realized/Unrealized Gains (Losses) Included in Earnings	(4)	(6)
Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	(2)	4
Purchases	0	0
Issuances	(74)	0
Settlements	35	80
Transfers Into Level 3	0	0
Transfers Out of Level 3	7	25
Total liabilities, ending balance	(331)	(270)
Current Period Unrealized Gains (Losses) Still Held Included in Earnings	(3)	(2)
Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income (Loss)	(2)	4
Long-term debt | Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total liabilities, beginning balance	(1,919)	(2,639)
Total Realized/Unrealized Gains (Losses) Included in Earnings	(107)	(166)
Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	(2)	22
Purchases	0	0
Issuances	(327)	(189)
Settlements	281	175
Transfers Into Level 3	(13)	(1)
Transfers Out of Level 3	128	403
Total liabilities, ending balance	(1,959)	(2,395)
Current Period Unrealized Gains (Losses) Still Held Included in Earnings	(69)	(119)
Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income (Loss)	(2)	22
Loans held for sale | Loans | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total assets, beginning balance	32	49
Assets, Total Realized/Unrealized Gains (Losses) Included in Earnings	1	0
Assets, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss)	0	0
Assets, Purchases	17	1
Assets, Issuances	0	0
Assets, Settlements	(24)	0
Assets, Transfers Into Level 3	3	0
Assets Transfers out of Level 3	(4)	0
Total assets, ending balance	25	50
Assets, Current Period Unrealized Gains (Losses) Still Held Included in Earnings	1	0
Assets, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income (Loss)	$ 0	$ 0