Derivative instruments - Gains (Losses) Related to Hedging Derivative Portfolio Recognized in the Income Statement (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2022	Jun. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Derivative Instruments, Gain (Loss) [Line Items]
(Loss) gain recognized in the consolidated income statement due to fair value and cash flow hedging relationships	$ (3)	$ 7	$ 1	$ 7	$ 13
Interest rate contracts \| Securities available-for-sale \| Interest revenue
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (loss) recognized on derivatives	1,294	866	183	3,644	649
Gain or (loss) recognized on hedged item	(1,292)	(858)	(184)	(3,630)	(647)
Interest rate contracts \| Long-term debt \| Interest expense
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (loss) recognized on derivatives	(540)	(292)	(96)	(1,573)	(427)
Gain or (loss) recognized on hedged item	539	291	96	1,570	426
FX contracts \| Staff expense
Derivative Instruments, Gain (Loss) [Line Items]
Loss (gain) on cash flow hedges	(3)	(1)	2	(4)	11
FX contracts \| Investment and other income
Derivative Instruments, Gain (Loss) [Line Items]
Loss (gain) on cash flow hedges	(1)	0	0	(1)	0
FX contracts \| Securities available-for-sale
Derivative Instruments, Gain (Loss) [Line Items]
Gain from components excluded from assessment of fair value hedge effectiveness, net (less than)	1	1	1	1	1
FX contracts \| Securities available-for-sale \| Foreign exchange revenue
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (loss) recognized on derivatives	(2)	(1)	0	(4)	7
Gain or (loss) recognized on hedged item	$ 2	$ 2	$ 0	$ 5	$ (6)

Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement.

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Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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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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Amount, before tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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