Derivative Instruments and Hedging Activities - Gains (Losses) on Accounting Hedges and Fair Value Hedges (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Investment Securities—AFS
Investment Securities—AFS and Deposits
Amortized cost basis currently/ carrying amount currently or previously hedged	$ 17,902	$ 16,288
Basis adjustments included in amortized cost/ carrying amount	(591)	(39)
Deposits
Investment Securities—AFS and Deposits
Amortized cost basis currently/ carrying amount currently or previously hedged	6,279	15,059
Basis adjustments included in amortized cost/ carrying amount	5	93
Borrowings
Borrowings
Carrying amount currently or previously hedged	122,919	114,349
Basis adjustments included in carrying amount—Outstanding hedges	2,324	6,575
Basis adjustments included in carrying amount—Terminated hedges	(743)	(756)
Fair Value Hedges \| Interest Income \| Interest rate
Gain (Loss) on Fair Value Hedges Recognized in Interest Income / Expense
Gains (losses) recognized in Interest Income / Expense	742	75	$ (10)
Fair Value Hedges \| Interest Income \| Investment Securities—AFS
Gain (Loss) on Fair Value Hedges Recognized in Interest Income / Expense
Gains (losses) recognized in Interest Income / Expense	(629)	(33)	10
Fair Value Hedges \| Interest expense \| Interest rate
Gain (Loss) on Fair Value Hedges Recognized in Interest Income / Expense
Gains (losses) recognized in Interest Income / Expense	(4,306)	4,678	4,212
Fair Value Hedges \| Interest expense \| Deposits
Gain (Loss) on Fair Value Hedges Recognized in Interest Income / Expense
Gains (losses) recognized in Interest Income / Expense	88	(100)	7
Fair Value Hedges \| Interest expense \| Borrowings
Gain (Loss) on Fair Value Hedges Recognized in Interest Income / Expense
Gains (losses) recognized in Interest Income / Expense	4,214	(4,692)	(4,288)
Net Investment Hedges \| Foreign exchange
Net Investment Hedges
Recognized in OCI	664	(366)	14
Forward points excluded from hedge effectiveness testing—Recognized in Interest income	$ (53)	$ 16	$ 136

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