Derivative Instruments and Hedging Activities - Effects of Fair Value and Cash Flow Hedge Accounting (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Derivative Instruments, Gain (Loss) [Line Items]
Interest and dividend income, securities	$ 627	$ 499	$ 1,881	$ 1,336
Interest and fee income, loans	9,696	7,578	27,476	20,550
Interest and dividend income, other	550	123	1,436	193
Deposits	(2,611)	(689)	(6,744)	(1,200)
Securitized debt obligations	(249)	(120)	(696)	(214)
Senior and subordinated notes	(579)	(319)	(1,596)	(644)
Non-interest income (loss)	256	192	730	634
Amortization expense (benefit)	(20)	(23)	(56)	(57)
Loss (net after-tax) recorded in AOCI related to derivatives designated as cash flow hedges expected to be reclassified to earnings over the next 12 months			$ 877
Maximum length of time over which forecasted transactions were hedged, years			9 years 6 months
Non interest income - Other
Derivative Instruments, Gain (Loss) [Line Items]
Realized losses (gains) on foreign exchange contracts reclassified from AOCI	100	79	$ 70	98
Cash flow hedges | Interest income - Investment securities
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on cash flow hedges	0	0	0	0
Cash flow hedges | Interest income - Loans
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on cash flow hedges	(320)	(86)	(879)	104
Cash flow hedges | Interest income - Other
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on cash flow hedges	3	2	9	1
Cash flow hedges | Interest expense - Deposits
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on cash flow hedges	0	0	0	0
Cash flow hedges | Interest expense - Securitized Debt Obligation
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on cash flow hedges	0	0	0	0
Cash flow hedges | Interest expense - Senior and Subordinated Debt
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on cash flow hedges	0	0	0	0
Cash flow hedges | Non interest income - Other
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on cash flow hedges	1	(1)	1	(1)
Cash flow hedges | Interest rate contracts | Interest income - Investment securities
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification adjustment from AOCI on derivatives, net of tax	0	0	0	0
Cash flow hedges | Interest rate contracts | Interest income - Loans
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification adjustment from AOCI on derivatives, net of tax	(320)	(86)	(879)	104
Cash flow hedges | Interest rate contracts | Interest income - Other
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification adjustment from AOCI on derivatives, net of tax	0	0	0	0
Cash flow hedges | Interest rate contracts | Interest expense - Deposits
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification adjustment from AOCI on derivatives, net of tax	0	0	0	0
Cash flow hedges | Interest rate contracts | Interest expense - Securitized Debt Obligation
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification adjustment from AOCI on derivatives, net of tax	0	0	0	0
Cash flow hedges | Interest rate contracts | Interest expense - Senior and Subordinated Debt
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification adjustment from AOCI on derivatives, net of tax	0	0	0	0
Cash flow hedges | Interest rate contracts | Non interest income - Other
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification adjustment from AOCI on derivatives, net of tax	0	0	0	0
Cash flow hedges | Foreign exchange contracts | Interest income - Investment securities
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification adjustment from AOCI on derivatives, net of tax	0	0	0	0
Cash flow hedges | Foreign exchange contracts | Interest income - Loans
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification adjustment from AOCI on derivatives, net of tax	0	0	0	0
Cash flow hedges | Foreign exchange contracts | Interest income - Other
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification adjustment from AOCI on derivatives, net of tax	3	2	9	1
Cash flow hedges | Foreign exchange contracts | Interest expense - Deposits
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification adjustment from AOCI on derivatives, net of tax	0	0	0	0
Cash flow hedges | Foreign exchange contracts | Interest expense - Securitized Debt Obligation
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification adjustment from AOCI on derivatives, net of tax	0	0	0	0
Cash flow hedges | Foreign exchange contracts | Interest expense - Senior and Subordinated Debt
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification adjustment from AOCI on derivatives, net of tax	0	0	0	0
Cash flow hedges | Foreign exchange contracts | Non interest income - Other
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification adjustment from AOCI on derivatives, net of tax	1	(1)	1	(1)
Fair value hedges | Interest income - Investment securities
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on fair value hedges	21	3	56	(48)
Fair value hedges | Interest income - Loans
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on fair value hedges	0	0	0	0
Fair value hedges | Interest income - Other
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on fair value hedges	0	0	0	0
Fair value hedges | Interest expense - Deposits
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on fair value hedges	(104)	4	(281)	47
Fair value hedges | Interest expense - Securitized Debt Obligation
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on fair value hedges	(112)	(20)	(298)	12
Fair value hedges | Interest expense - Senior and Subordinated Debt
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on fair value hedges	(236)	(33)	(643)	94
Fair value hedges | Non interest income - Other
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on fair value hedges	0	0	0	(1)
Fair value hedges | Interest rate contracts | Interest income - Investment securities
Derivative Instruments, Gain (Loss) [Line Items]
Interest recognized on derivatives	42	22	113	22
Gains (losses) recognized on derivatives	(15)	83	(35)	294
Gains (losses) recognized on hedged items	(6)	(102)	(22)	(364)
Excluded component of fair value hedges	0	0	0	0
Fair value hedges | Interest rate contracts | Interest income - Loans
Derivative Instruments, Gain (Loss) [Line Items]
Interest recognized on derivatives	0	0	0	0
Gains (losses) recognized on derivatives	0	0	0	0
Gains (losses) recognized on hedged items	0	0	0	0
Excluded component of fair value hedges	0	0	0	0
Fair value hedges | Interest rate contracts | Interest income - Other
Derivative Instruments, Gain (Loss) [Line Items]
Interest recognized on derivatives	0	0	0	0
Gains (losses) recognized on derivatives	0	0	0	0
Gains (losses) recognized on hedged items	0	0	0	0
Excluded component of fair value hedges	0	0	0	0
Fair value hedges | Interest rate contracts | Interest expense - Deposits
Derivative Instruments, Gain (Loss) [Line Items]
Interest recognized on derivatives	(104)	4	(278)	46
Gains (losses) recognized on derivatives	(38)	(381)	(84)	(569)
Gains (losses) recognized on hedged items	38	381	81	570
Excluded component of fair value hedges	0	0	0	0
Fair value hedges | Interest rate contracts | Interest expense - Securitized Debt Obligation
Derivative Instruments, Gain (Loss) [Line Items]
Interest recognized on derivatives	(112)	(21)	(297)	12
Gains (losses) recognized on derivatives	4	(311)	(10)	(735)
Gains (losses) recognized on hedged items	(4)	312	9	735
Excluded component of fair value hedges	0	0	0	0
Fair value hedges | Interest rate contracts | Interest expense - Senior and Subordinated Debt
Derivative Instruments, Gain (Loss) [Line Items]
Interest recognized on derivatives	(275)	(71)	(754)	(20)
Gains (losses) recognized on derivatives	(273)	(807)	(275)	(2,039)
Gains (losses) recognized on hedged items	313	846	388	2,155
Excluded component of fair value hedges	(1)	(1)	(2)	(2)
Fair value hedges | Interest rate contracts | Non interest income - Other
Derivative Instruments, Gain (Loss) [Line Items]
Interest recognized on derivatives	0	0	0	0
Gains (losses) recognized on derivatives	(42)	(85)	(17)	(197)
Gains (losses) recognized on hedged items	42	85	17	196
Excluded component of fair value hedges	$ 0	$ 0	$ 0	$ 0