Derivative Instruments and Hedging Activities - Derivative Assets and Liabilities at Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Notional or contractual amount	$ 233,333	$ 232,327
Derivative assets, gross amount	3,716	3,415
Derivative liabilities, gross amount	2,410	1,518
Derivative asset, netting adjustments	(964)	(1,148)
Derivative liability, netting adjustments	(850)	(739)
Total derivative assets	2,752	2,267
Total derivative liabilities	1,560	779
Net valuation allowance on derivative assets and liabilities for non-performance risk	23	31
Derivatives designated as accounting hedges
Derivatives, Fair Value [Line Items]
Notional or contractual amount	140,373	138,724
Derivative assets, gross amount	604	921
Derivative liabilities, gross amount	196	368
Derivatives designated as accounting hedges \| Interest rate contracts
Derivatives, Fair Value [Line Items]
Notional or contractual amount	131,261	129,499
Derivative assets, gross amount	486	757
Derivative liabilities, gross amount	19	11
Derivatives designated as accounting hedges \| Interest rate contracts \| Fair value hedges
Derivatives, Fair Value [Line Items]
Notional or contractual amount	44,361	47,349
Derivative assets, gross amount	5	9
Derivative liabilities, gross amount	7	10
Derivatives designated as accounting hedges \| Interest rate contracts \| Cash flow hedges
Derivatives, Fair Value [Line Items]
Notional or contractual amount	86,900	82,150
Derivative assets, gross amount	481	748
Derivative liabilities, gross amount	12	1
Derivatives designated as accounting hedges \| Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Notional or contractual amount	9,112	9,225
Derivative assets, gross amount	118	164
Derivative liabilities, gross amount	177	357
Derivatives designated as accounting hedges \| Foreign exchange contracts \| Fair value hedges
Derivatives, Fair Value [Line Items]
Notional or contractual amount	1,482	1,527
Derivative assets, gross amount	83	164
Derivative liabilities, gross amount	0	0
Derivatives designated as accounting hedges \| Foreign exchange contracts \| Cash flow hedges
Derivatives, Fair Value [Line Items]
Notional or contractual amount	4,233	4,582
Derivative assets, gross amount	35	0
Derivative liabilities, gross amount	33	161
Derivatives designated as accounting hedges \| Foreign exchange contracts \| Net investment hedges
Derivatives, Fair Value [Line Items]
Notional or contractual amount	3,397	3,116
Derivative assets, gross amount	0	0
Derivative liabilities, gross amount	144	196
Derivatives not designated as accounting hedges
Derivatives, Fair Value [Line Items]
Notional or contractual amount	92,960	93,603
Derivative assets, gross amount	3,112	2,494
Derivative liabilities, gross amount	2,214	1,150
Derivatives not designated as accounting hedges \| Customer accommodation
Derivatives, Fair Value [Line Items]
Notional or contractual amount	89,763	90,007
Derivative assets, gross amount	3,067	2,422
Derivative liabilities, gross amount	2,167	1,088
Derivatives not designated as accounting hedges \| Interest rate contracts \| Customer accommodation
Derivatives, Fair Value [Line Items]
Notional or contractual amount	68,537	68,459
Derivative assets, gross amount	935	1,429
Derivative liabilities, gross amount	173	198
Derivatives not designated as accounting hedges \| Interest rate contracts \| Other interest rate exposures
Derivatives, Fair Value [Line Items]
Notional or contractual amount	1,209	1,770
Derivative assets, gross amount	45	71
Derivative liabilities, gross amount	46	56
Derivatives not designated as accounting hedges \| Foreign exchange contracts \| Customer accommodation
Derivatives, Fair Value [Line Items]
Notional or contractual amount	4,450	4,677
Derivative assets, gross amount	39	58
Derivative liabilities, gross amount	31	70
Derivatives not designated as accounting hedges \| Commodity contracts \| Customer accommodation
Derivatives, Fair Value [Line Items]
Notional or contractual amount	16,776	16,871
Derivative assets, gross amount	2,093	935
Derivative liabilities, gross amount	1,963	820
Derivatives not designated as accounting hedges \| Other contracts
Derivatives, Fair Value [Line Items]
Notional or contractual amount	1,988	1,826
Derivative assets, gross amount	0	1
Derivative liabilities, gross amount	$ 1	$ 6

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Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, and obligation to return cash collateral under master netting arrangements.

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