Derivative Instruments and Hedging Activities - Effects of Fair Value and Cash Flow Hedge Accounting (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Interest and dividend income, securities	$ 443	$ 583	$ 1,455	$ 1,867
Interest and fee income, loans	5,758	6,429	18,120	19,180
Interest and dividend income, other	14	63	67	196
Deposits	(476)	(901)	(1,818)	(2,588)
Securitized debt obligations	(43)	(123)	(198)	(405)
Senior and subordinated notes	(132)	(299)	(551)	(923)
Non-interest income	706	144	1,017	492
Amortization of basis adjustment	19	(60)	(34)	(177)
Non interest income - Other
Derivative Instruments, Gain (Loss) [Line Items]
Realized losses (gains) on foreign exchange contracts reclassified from AOCI	73	(71)	(20)	224
Fair value hedges \| Interest income - Investment securities
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on fair value hedges	(30)	(2)	(62)	(3)
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	45	(26)	70	(89)
Fair value hedges \| Interest expense - Securitized Debt Obligation
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on fair value hedges	33	(21)	62	(80)
Fair value hedges \| Interest expense - Senior and Subordinated Debt
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on fair value hedges	94	(49)	173	(149)
Fair value hedges \| Non interest income - Other
Derivative Instruments, Gain (Loss) [Line Items]
Net income (expense) recognized on fair value hedges	0	(2)	0	(1)
Fair value hedges \| Interest rate contracts \| Interest income - Investment securities
Derivative Instruments, Gain (Loss) [Line Items]
Interest recognized on derivatives	(23)	(3)	(51)	(2)
Gains (losses) recognized on derivatives	24	(80)	(340)	(366)
Gains (losses) recognized on hedged items	(31)	81	329	365
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	44	(26)	69	(95)
Gains (losses) recognized on derivatives	(47)	46	249	295
Gains (losses) recognized on hedged items	48	(46)	(248)	(289)
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	40	(5)	92	(17)
Gains (losses) recognized on derivatives	(48)	(10)	221	102
Gains (losses) recognized on hedged items	41	(6)	(251)	(165)
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	56	(3)	166	(24)
Gains (losses) recognized on derivatives	(72)	216	1,057	968
Gains (losses) recognized on hedged items	111	(261)	(1,048)	(1,092)
Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net	(1)	(1)	(2)	(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	61	(60)	64	(49)
Gains (losses) recognized on hedged items	(61)	58	(64)	48
Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net	0	0	0	0
Cash flow hedges \| Interest income - Investment securities
Derivative Instruments, Gain (Loss) [Line Items]
Net income recognized on cash flow hedges	8	(1)	17	(8)
Cash flow hedges \| Interest income - Loans
Derivative Instruments, Gain (Loss) [Line Items]
Net income recognized on cash flow hedges	171	(43)	330	(158)
Cash flow hedges \| Interest income - Other
Derivative Instruments, Gain (Loss) [Line Items]
Net income recognized on cash flow hedges	1	12	10	37
Cash flow hedges \| Interest expense - Deposits
Derivative Instruments, Gain (Loss) [Line Items]
Net income 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 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 recognized on cash flow hedges	0	0	0	0
Cash flow hedges \| Non interest income - Other
Derivative Instruments, Gain (Loss) [Line Items]
Net income recognized on cash flow hedges	0	1	(2)	0
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	8	(1)	17	(8)
Cash flow hedges \| Interest rate contracts \| Interest income - Loans
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification adjustment from AOCI on derivatives, net of tax	171	(43)	330	(158)
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	12	10	37
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	$ (2)	$ 0

Amortization of basis adjustment

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Total amount of gain (loss) derived from cash flow hedges recognized in earnings in the period

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Interest Expense, Secured Debt

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Realized Gains (Losses) on Foreign Exchange Contracts Reclassified from AOCI

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Net gain (loss) relating to components of the gain (loss) on the fair value hedging instrument excluded from the assessment of fair value hedge effectiveness. Recognized in earnings.

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Total amount of gain (loss) derived from fair value hedges recognized in earnings in the period.

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