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Shareholders' Equity - Disclosure of Share Capital (Detail) - shares
shares in Thousands
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Class B treasury shares [member]      
Disclosure of treasury shares [line items]      
Weighted average number of treasury shares B 13,070 14,415 9,841
Subsidiaries [member]      
Disclosure of treasury shares [line items]      
Weighted average number of treasury shares B 56,467 60,129 38,490