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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Restructuring expenses and disposition of assets (Details) - USD ($) $ in Thousands | 12 Months Ended | 15 Months Ended
--- | --- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | Mar. 31, 2024
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Restructuring Charges, Total | $ 3,535 | $ 11,228 |  |
Gain (loss) on disposal of fixed asset | 13,300 |  |  |
Proceeds from sale of assets | 18,609 |  | $ 1,067 |
Book value of fixed asset | 1,040,193 | 1,080,659 |  |
Disposal | Non-core fixed asset |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Gain (loss) on disposal of fixed asset | 15,500 |  |  |
Proceeds from sale of assets | 17,800 |  |  |
Book value of fixed asset | 500 |  |  |
Transaction costs | 1,800 |  |  |
Corporate and Other |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Restructuring Charges, Total | 879 |  |  |
Book value of fixed asset | 7,707 | 4,915 |  |
2023 Restructuring |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Employee termination benefits |  |  |  | $ 6,641
Contract termination costs |  |  |  | 5,777
Restructuring Charges, Total | 1,200 | 11,200 |  | 12,418
Restructure costs paid | 11,900 |  |  |
Gain on lease termination | 300 |  |  |
Restructuring costs remain accrued | 800 |  |  |
Right of use assets terminated | 5,600 |  |  |
Lease liabilities terminated | 5,900 |  |  |
2024 Reorganization |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Contract termination costs | 2,300 |  |  |
Restructure costs paid | 1,600 |  |  |
Restructuring costs remain accrued | 700 |  |  |
2024 Reorganization | Corporate and Other |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Contract termination costs | 900 |  |  |
US Telecom |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Gain (loss) on disposal of fixed asset | (2,500) |  |  |
US Telecom | Operating segments |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Restructuring Charges, Total | 1,167 | 7,737 |  |
Book value of fixed asset | 565,625 | 593,833 |  |
US Telecom | 2023 Restructuring |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Employee termination benefits |  |  |  | 1,960
Contract termination costs |  |  |  | 5,777
Restructuring Charges, Total |  |  |  | 7,737
US Telecom | 2024 Reorganization | Operating segments |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Contract termination costs | 1,100 |  |  |
International Telecom | Disposal | Non-core fixed asset |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Gain (loss) on disposal of fixed asset | 15,500 |  |  |
Proceeds from sale of assets | 17,800 |  |  |
Book value of fixed asset | 500 |  |  |
Transaction costs | 1,800 |  |  |
International Telecom | Operating segments |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Restructuring Charges, Total | 1,489 | 3,491 |  |
Book value of fixed asset | 466,861 | $ 481,911 |  |
International Telecom | 2023 Restructuring |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Employee termination benefits |  |  |  | 4,681
Restructuring Charges, Total |  |  |  | $ 4,681
International Telecom | 2024 Reorganization | Operating segments |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Contract termination costs | $ 300 |  |  |

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