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Shareholders' equity - Summary of Calculation of Dividends and Interest on Capital (Parenthetical) (Detail) | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Disclosure of Dividends [abstract] |  |  |
Legal reserve, percentage | 5.00% | 5.00% | 5.00%
Mandatory minimum dividend, percentage | 25.00% | 25.00% | 25.00%

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- Definition Disclosure of dividends. + References No definition available. + Details
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- Definition Legal reserve percentage. + References No definition available. + Details
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- Definition Mandatory minimum dividend percentage. + References No definition available. + Details
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Balance Type: | na
Period Type: | duration