Derivative Instruments and Hedging Activities - Derivative Assets and Liabilities at Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Notional or contractual amount	$ 231,927	$ 232,327
Derivative assets, gross amount	2,869	3,415
Derivative liabilities, gross amount	1,651	1,518
Derivative asset, netting adjustments	(844)	(1,148)
Derivative liability, netting adjustments	(679)	(739)
Total derivative assets	2,025	2,267
Total derivative liabilities	972	779
Net valuation allowance on derivative assets and liabilities for non-performance risk	26	31
Derivatives designated as accounting hedges
Derivatives, Fair Value [Line Items]
Notional or contractual amount	138,774	138,724
Derivative assets, gross amount	599	921
Derivative liabilities, gross amount	328	368
Derivatives designated as accounting hedges \| Interest rate contracts
Derivatives, Fair Value [Line Items]
Notional or contractual amount	130,030	129,499
Derivative assets, gross amount	509	757
Derivative liabilities, gross amount	52	11
Derivatives designated as accounting hedges \| Interest rate contracts \| Fair value hedges
Derivatives, Fair Value [Line Items]
Notional or contractual amount	45,880	47,349
Derivative assets, gross amount	6	9
Derivative liabilities, gross amount	22	10
Derivatives designated as accounting hedges \| Interest rate contracts \| Cash flow hedges
Derivatives, Fair Value [Line Items]
Notional or contractual amount	84,150	82,150
Derivative assets, gross amount	503	748
Derivative liabilities, gross amount	30	1
Derivatives designated as accounting hedges \| Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Notional or contractual amount	8,744	9,225
Derivative assets, gross amount	90	164
Derivative liabilities, gross amount	276	357
Derivatives designated as accounting hedges \| Foreign exchange contracts \| Fair value hedges
Derivatives, Fair Value [Line Items]
Notional or contractual amount	1,466	1,527
Derivative assets, gross amount	84	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	4,106	4,582
Derivative assets, gross amount	6	0
Derivative liabilities, gross amount	81	161
Derivatives designated as accounting hedges \| Foreign exchange contracts \| Net investment hedges
Derivatives, Fair Value [Line Items]
Notional or contractual amount	3,172	3,116
Derivative assets, gross amount	0	0
Derivative liabilities, gross amount	195	196
Derivatives not designated as accounting hedges
Derivatives, Fair Value [Line Items]
Notional or contractual amount	93,153	93,603
Derivative assets, gross amount	2,270	2,494
Derivative liabilities, gross amount	1,323	1,150
Derivatives not designated as accounting hedges \| Customer accommodation
Derivatives, Fair Value [Line Items]
Notional or contractual amount	89,241	90,007
Derivative assets, gross amount	2,211	2,422
Derivative liabilities, gross amount	1,287	1,088
Derivatives not designated as accounting hedges \| Interest rate contracts \| Customer accommodation
Derivatives, Fair Value [Line Items]
Notional or contractual amount	68,333	68,459
Derivative assets, gross amount	935	1,429
Derivative liabilities, gross amount	210	198
Derivatives not designated as accounting hedges \| Interest rate contracts \| Other interest rate exposures
Derivatives, Fair Value [Line Items]
Notional or contractual amount	2,118	1,770
Derivative assets, gross amount	59	71
Derivative liabilities, gross amount	33	56
Derivatives not designated as accounting hedges \| Foreign exchange contracts \| Customer accommodation
Derivatives, Fair Value [Line Items]
Notional or contractual amount	4,027	4,677
Derivative assets, gross amount	42	58
Derivative liabilities, gross amount	38	70
Derivatives not designated as accounting hedges \| Commodity contracts \| Customer accommodation
Derivatives, Fair Value [Line Items]
Notional or contractual amount	16,881	16,871
Derivative assets, gross amount	1,234	935
Derivative liabilities, gross amount	1,039	820
Derivatives not designated as accounting hedges \| Other contracts
Derivatives, Fair Value [Line Items]
Notional or contractual amount	1,794	1,826
Derivative assets, gross amount	0	1
Derivative liabilities, gross amount	$ 3	$ 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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