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Financial Risks - Summary of Exchange Rates of US Dollar and UK Pound per Euro (Detail)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
USD [member]          
Disclosure of foreign exchange rates [line items]          
Closing rates 1.12 1.14 1.20 1.05 1.09
GBP [member]          
Disclosure of foreign exchange rates [line items]          
Closing rates 0.85 0.90 0.89 0.85 0.74