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COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2019 | Dec. 31, 2011
Contingency related to spectrum fees |  |
Commitments and contingencies |  |
Spectrum fees paid |  | $ 2.6
Litigation proceedings and disputes in Guyana |  |
Commitments and contingencies |  |
Period for which litigation proceedings and other disputes have not been the subject of discussions or other significant activity | 5 years |
Legal claims regarding tax filings with the Guyana Revenue Authority |  |
Commitments and contingencies |  |
Future payments related to disputed tax assessments | $ 44.1 |
Accrued contingent liability | $ 5.0 |
Legal claims regarding tax filings with the Guyana Revenue Authority | Minimum |  |
Commitments and contingencies |  |
Percentage of return on investment ensured by the government of Guyana | 15.00% |

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