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Equity - Additional Information (Detail)
shares in Millions
 12 Months Ended
Dec. 31, 2017
$ / shares
shares
Dec. 31, 2016
$ / shares
shares
Disclosure of classes of share capital [line items]    
Common shares par value | $ / shares $ 10 $ 10
Shares allocated for exercise of employee stock options 500,000,000 500,000,000
Issued capital 25,930.3 25,930.3
Legal capital reserve percentage   10.00%
Percentage of paid in capital on reserve used to offset deficit or distribute as dividend in cash or stock 25.00%  
Top of range [member]    
Disclosure of classes of share capital [line items]    
Total distribution 50.00%  
American Depositary Shares (one represents five common shares) [member]    
Disclosure of classes of share capital [line items]    
Issued capital 1,068.2  
Number of shares issued 5,340.8