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Equity - Summary of Capital Stock (Detail) - shares
shares in Thousands
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Disclosure of classes of share capital [line items]      
Capital stock 2,100,832 2,072,922 2,072,922
Series A shares [member]      
Disclosure of classes of share capital [line items]      
Capital stock 992,078 992,078 992,078
Series D share [member]      
Disclosure of classes of share capital [line items]      
Capital stock 583,546 583,546 583,546
Series L share [member]      
Disclosure of classes of share capital [line items]      
Capital stock 525,208 497,298 497,298