Employee compensation and benefits - Share-based payments (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Compensation And Benefits [Abstract]
Expense from equity-settled share-based payment transactions in which goods or services received did not qualify for recognition as assets	$ 500	$ 534	$ 757
Disclosure of terms and conditions of share-based payment arrangement [line items]
Expense from share-based payments	546	624	791
Restricted share awards
Disclosure of terms and conditions of share-based payment arrangement [line items]
Expense from share-based payments	520	591	748
Savings-related and other share award option plans
Disclosure of terms and conditions of share-based payment arrangement [line items]
Expense from share-based payments	$ 26	$ 33	$ 43

Employee Compensation And Benefits [Abstract]

No definition available.

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- Definition

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

+ References

No definition available.

+ Details

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- Definition

The amount of expense arising from equity-settled share-based payment transactions in which the goods or services received did not qualify for recognition as assets. [Refer: Expense from share-based payment transactions in which goods or services received did not qualify for recognition as assets]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2017-01-01
-Paragraph 51
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_51_a&doctype=Standard
-URIDate 2017-03-09

+ Details

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- Definition

The amount of expense arising from share-based payment transactions in which the goods or services received did not qualify for recognition as assets.

+ References

+ Details

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- Details

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