Basis of preparation and recent accounting developments - Treatment of interests in Quadgas HoldCo Limited (Quadgas) (Details)	1 Months Ended
Jun. 30, 2019
UK Gas Distribution (Cadent)
Disclosure of subsidiaries [line items]
Proportion of ownership interest disposed	39.00%

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.

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