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5 Risk management (Details) ¥ in Thousands, R$ in Thousands, $ in Thousands | 12 Months Ended
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Dec. 31, 2020 BRL (R$) | Dec. 31, 2020 USD ($) | Dec. 31, 2020 JPY (¥) | Dec. 31, 2019 BRL (R$) | Dec. 31, 2019 USD ($) | Dec. 31, 2019 JPY (¥)
Summary of risk management [Line Items] |  |  |  |  |  |
Total exposure | R$ 3,563,170 |  |  | R$ 6,382,009 |  |
Total foreign currency-denominated borrowings | 3,547,862 |  |  | 6,358,798 |  |
USD |  |  |  |  |  |
Summary of risk management [Line Items] |  |  |  |  |  |
Borrowings and financing | 870,338 |  |  | 4,239,817 |  |
Interest and charges from borrowings and financing | 5,540 |  |  | 32,242 |  |
Borrowing cost | (12,342) |  |  | (20,173) |  |
USD | Foreign currency [member] |  |  |  |  |  |
Summary of risk management [Line Items] |  |  |  |  |  |
Borrowings and financing | $ |  | $ 167,479 |  |  | $ 1,051,881 |
Yen |  |  |  |  |  |
Summary of risk management [Line Items] |  |  |  |  |  |
Borrowings and financing | 2,671,255 |  |  | 2,097,225 |  |
Interest and charges from borrowings and financing | 16,037 |  |  | 12,725 |  |
Borrowing cost | R$ (2,966) |  |  | R$ (3,038) |  |
Yen | Foreign currency [member] |  |  |  |  |  |
Summary of risk management [Line Items] |  |  |  |  |  |
Borrowings and financing | ¥ |  |  | ¥ 52,969,560 |  |  | ¥ 56,452,885

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