Employee compensation and benefits - HSBC share option plans (Details) - Savings-related Share Option Plans - GBP (£)	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Disclosure of terms and conditions of share-based payment arrangement [line items]
Employee monthly savings	£ 500
Term of options granted for share-based payment arrangements	6 months
Exercise price discount	20.00%	20.00%
Minimum
Disclosure of terms and conditions of share-based payment arrangement [line items]
Award vesting period	3 years
Maximum
Disclosure of terms and conditions of share-based payment arrangement [line items]
Award vesting period	5 years

Share-Based Compensation Arrangement By Share-Based Payment Award, Award Vesting Period2

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Share-based Compensation Arrangement By Share-based Payment Award, Discount From Market Price, Offering Date

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Share-based Compensation Arrangement, Employee Monthly Savings

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Term Of Options Granted For Share-based Payment Arrangements

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Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table.

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