Investments in Joint Ventures and Associates - Summary of Individually Immaterial Joint Ventures (Detail) - GBP (£) £ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure of associates [line items]
Profit for the year	£ 266	£ 590	£ 408
Total comprehensive income	49	714	£ 253
Aggregated individually immaterial joint ventures [member]
Disclosure of associates [line items]
Profit for the year	0	1
Total comprehensive income	£ 0	£ 1

The amount of change in equity resulting from transactions and other events, other than those changes resulting from transactions with owners in their capacity as owners.

The total of income less expenses from continuing and discontinued operations, excluding the components of other comprehensive income. [Refer: Other comprehensive income]

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