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5. Risk Management (Details) ¥ in Thousands, R$ in Thousands, $ in Thousands | Dec. 31, 2017 BRL (R$) | Dec. 31, 2017 USD ($) | Dec. 31, 2017 JPY (¥) | Dec. 31, 2016 BRL (R$) | Dec. 31, 2016 USD ($) | Dec. 31, 2016 JPY (¥)
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SummaryOfRiskManagementLineItems [Line Items] |  |  |  |  |  |
Borrowings and financing - US | R$ 3,972,200 |  |  | R$ 4,047,682 |  |
Borrowings and financing - Yen | 1,692,713 |  |  | 1,609,419 |  |
Interest and charges from borrowings and financing - US$ | 26,628 |  |  | 25,114 |  |
Interest and charges from borrowings and financing - Yen | 10,834 |  |  | 10,769 |  |
Total exposure | 5,702,375 |  |  | 5,692,984 |  |
Borrowing cost - US | (26,454) |  |  | (29,650) |  |
Borrowing cost - Yen | (3,100) |  |  | (2,971) |  |
Total foreign currency-denominated borrowings | R$ 5,672,821 |  |  | R$ 5,660,363 |  |
Foreign currency |  |  |  |  |  |
SummaryOfRiskManagementLineItems [Line Items] |  |  |  |  |  |
Borrowings and financing - US | $ |  | $ 1,200,786 |  |  | $ 1,241,963 |
Borrowings and financing - Yen | ¥ |  |  | ¥ 57,575,271 |  |  | ¥ 57,643,930

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