Fair values of financial instruments carried at fair value - Quantitative information about significant unobservable inputs in Level 3 valuations (Details) - Recurring fair value measurement $ in Millions	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)
Prepayment rate | Model – Discounted cash flow | Minimum | Interest rate | securitisation swaps
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Significant unobservable input, assets, percentage	0.05	0.05
Prepayment rate | Model – Discounted cash flow | Maximum | Interest rate | securitisation swaps
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Significant unobservable input, assets, percentage	0.10	0.10
Bid quotes | Market proxy | Minimum | – collateralised loan/debt obligation
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Significant unobservable input, assets, percentage	0	0
Bid quotes | Market proxy | Minimum | – other ABSs
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Significant unobservable input, assets, percentage	0	0
Bid quotes | Market proxy | Maximum | – collateralised loan/debt obligation
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Significant unobservable input, assets, percentage	89	92
Bid quotes | Market proxy | Maximum | – other ABSs
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Significant unobservable input, assets, percentage	98	99
Equity volatility | Model – Option model | Minimum | Equities | long-dated single stock options
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Significant unobservable input, assets, percentage	0.07	0.07
Equity volatility | Model – Option model | Maximum | Equities | long-dated single stock options
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Significant unobservable input, assets, percentage	0.77	1.53
FX volatility | Model – Option model | Minimum | Foreign exchange | FX options
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Significant unobservable input, assets, percentage	0.02	0.01
FX volatility | Model – Option model | Maximum | Foreign exchange | FX options
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Significant unobservable input, assets, percentage	0.44	0.46
Interest rate volatility | Model – Option model | Minimum | Interest rate | long-dated swaptions
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Significant unobservable input, assets, percentage	0.09	0.08
Interest rate volatility | Model – Option model | Maximum | Interest rate | long-dated swaptions
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Significant unobservable input, assets, percentage	0.34	0.53
Interest rate volatility | Model – Discounted cash flow | Minimum | – repurchase agreements
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Significant unobservable input, assets, percentage	0	0.01
Interest rate volatility | Model – Discounted cash flow | Maximum | – repurchase agreements
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Significant unobservable input, assets, percentage	0.10	0.09
Level 3
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	$ 27,230	$ 27,149
Financial liabilities	12,915	13,826
Level 3 | Private equity including strategic investments
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	128
Level 3 | Asset-backed securities
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	0	0
Level 3 | Structured notes
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	10,149	10,432
Level 3 | Other derivatives
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	2,315	2,920
Level 3 | Other portfolios
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	323	382
Level 3 | – other
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	28
Level 3 | Private equity including strategic investments
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	17,392	16,319
Level 3 | Asset-backed securities
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	747	741
Level 3 | – collateralised loan/debt obligation
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	76
Level 3 | – other ABSs
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	671
Level 3 | Structured notes
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	3	$ 0
Level 3 | – equity-linked notes
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	3
Level 3 | – Foreign exchange (‘FX’)-linked notes
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	0
Level 3 | – other
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	0
Level 3 | Other derivatives
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	1,772
Level 3 | long-dated single stock options
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	7,316
Level 3 | – repurchase agreements
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	763
Financial liabilities	295
Level 3 | – other
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	6,553
Level 3 | Interest rate
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	511
Financial liabilities	718
Level 3 | Interest rate | securitisation swaps
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	160
Level 3 | Interest rate | long-dated swaptions
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	75
Level 3 | Interest rate | – other
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	483
Level 3 | Interest rate | securitisation swaps
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	114
Level 3 | Interest rate | long-dated swaptions
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	64
Level 3 | Interest rate | other
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	333
Level 3 | Foreign exchange
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	308
Financial liabilities	388
Level 3 | Foreign exchange | – other
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	70
Level 3 | Foreign exchange | FX options
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	318
Level 3 | Foreign exchange | other
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	37
Level 3 | Foreign exchange | FX options
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	271
Level 3 | Equities
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	737
Financial liabilities	941
Level 3 | Equities | – other
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	228
Level 3 | Equities | long-dated single stock options
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	713
Level 3 | Equities | other
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	217
Level 3 | Equities | long-dated single stock options
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	520
Level 3 | Credit
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	216
Financial liabilities	268
Level 3 | Credit | – other
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	268
Level 3 | Credit | other
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	$ 216