Derivative Instruments and Hedging Activities - Effects of Fair Value and Cash Flow Hedge Accounting (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Derivative Instruments, Gain (Loss) [Line Items]
Interest and dividend income, securities	$ 435	$ 370	$ 837	$ 761
Interest and fee income, loans	6,605	5,753	12,972	11,607
Interest and dividend income, other	55	16	70	32
Deposits	(293)	(237)	(511)	(506)
Securitized debt obligations	(65)	(28)	(94)	(60)
Senior and subordinated notes	(194)	(122)	(325)	(251)
Non-interest income (loss)	99	231	442	353
Amortization expense (benefit)	(17)	(22)	(34)	(44)
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			$ 431
Maximum length of time over which forecasted transactions were hedged, years			5 years 8 months 12 days
Non interest income - Other
Derivative Instruments, Gain (Loss) [Line Items]
Realized losses (gains) on foreign exchange contracts reclassified from AOCI	31	77	$ 18	162
Cash flow hedges | Interest income - Investment securities
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on cash flow hedges	0	11	0	20
Cash flow hedges | Interest income - Loans
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on cash flow hedges	63	234	190	460
Cash flow hedges | Interest income - Other
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on cash flow hedges	(1)	0	(1)	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	0	1	0	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	11	0	20
Cash flow hedges | Interest rate contracts | Interest income - Loans
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification adjustment from AOCI on derivatives, net of tax	63	234	190	460
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	(1)	0	(1)	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	0	1	0	1
Fair value hedges | Interest income - Investment securities
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on fair value hedges	(17)	(32)	(51)	(62)
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	22	34	43	70
Fair value hedges | Interest expense - Securitized Debt Obligation
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on fair value hedges	7	24	32	52
Fair value hedges | Interest expense - Senior and Subordinated Debt
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on fair value hedges	50	89	127	182
Fair value hedges | Non interest income - Other
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on fair value hedges	(1)	0	(1)	0
Fair value hedges | Interest rate contracts | Interest income - Investment securities
Derivative Instruments, Gain (Loss) [Line Items]
Interest recognized on derivatives	8	(25)	0	(50)
Gains (losses) recognized on derivatives	36	11	211	111
Gains (losses) recognized on hedged items	(61)	(18)	(262)	(123)
Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net	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
Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net	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
Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net	0	0	0	0
Fair value hedges | Interest rate contracts | Interest expense - Deposits
Derivative Instruments, Gain (Loss) [Line Items]
Interest recognized on derivatives	21	34	42	70
Gains (losses) recognized on derivatives	(73)	(31)	(188)	(89)
Gains (losses) recognized on hedged items	74	31	189	89
Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net	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	6	30	33	63
Gains (losses) recognized on derivatives	(119)	(17)	(424)	(97)
Gains (losses) recognized on hedged items	120	11	423	86
Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net	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	13	56	51	118
Gains (losses) recognized on derivatives	(376)	0	(1,232)	(336)
Gains (losses) recognized on hedged items	413	33	1,309	401
Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net	0	0	(1)	(1)
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	(74)	16	(112)	(45)
Gains (losses) recognized on hedged items	73	(16)	111	45
Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net	$ 0	$ 0	$ 0	$ 0