XML 215 R138.htm IDEA: XBRL DOCUMENT v3.20.1
Derivative Financial Instruments and Hedge Accounting - Summary of Amounts Related to Items Designated as Hedging Instruments (Detail) - GBP (£)
£ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Disclosure of detailed information about hedges [line items]    
Hedging gains/(losses) recognised in OCI £ 3  
Financial liabilities - derivative financial instruments [member]    
Disclosure of detailed information about hedges [line items]    
Carrying amount of hedged instruments (21) £ (59)
Change in value of hedging instrument used to determine hedge ineffectiveness 13 (22)
Nominal amounts of hedging instruments (722) (607)
Hedging gains/(losses) recognised in OCI 13 (22)
Hedge ineffectiveness recognised in profit or loss 0 0
Financial liabilities - borrowings [member]    
Disclosure of detailed information about hedges [line items]    
Carrying amount of hedged instruments (246) (256)
Change in value of hedging instrument used to determine hedge ineffectiveness 10 (10)
Nominal amounts of hedging instruments (246) (256)
Hedging gains/(losses) recognised in OCI 10 (10)
Hedge ineffectiveness recognised in profit or loss £ 0 £ 0