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Stockholders' Equity - Summary of Appropriated Reserves (Detail) - BRL (R$) R$ in Millions | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | --- | ---
Disclosure of reserves within equity [line items] |  |  |
Capital reserves | R$ 285 | R$ 285 | R$ 285
Profit reserves | 12,663 | 13,195 | 12,214
Total reserves at parent company | 12,948 | 13,480 | 12,499
Premium on subscription of shares [Member] |  |  |
Disclosure of reserves within equity [line items] |  |  |
Capital reserves | 284 | 284 | 284
Reserves from tax incentives, restatement of equity securities and other [Member] |  |  |
Disclosure of reserves within equity [line items] |  |  |
Capital reserves | 1 | 1 | 1
Legal [Member] |  |  |
Disclosure of reserves within equity [line items] |  |  |
Profit reserves | 11,326 | 9,989 | 8,892
Statutory [Member] |  |  |
Disclosure of reserves within equity [line items] |  |  |
Profit reserves | 3,043 | (2,775) | 589
Corporate reorganizations [member] |  |  |
Disclosure of reserves within equity [line items] |  |  |
Profit reserves | (11,517) | (11,517) | (10,925)
Special profit reserves [member] |  |  |
Disclosure of reserves within equity [line items] |  |  |
Profit reserves | R$ 9,811 | R$ 17,498 | R$ 13,658

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