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Long-term debt: (Details) $ in Thousands, € in Millions |  |  |  |  |  | 1 Months Ended | 12 Months Ended |  |  |  |
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Jun. 15, 2024 | Jun. 11, 2024 USD ($) | May 02, 2024 USD ($) | Jun. 22, 2022 USD ($) | Jun. 22, 2022 EUR (€) | May 07, 2021 USD ($) | Dec. 31, 2024 USD ($) | Nov. 30, 2024 USD ($) | May 31, 2024 USD ($) | Nov. 30, 2023 USD ($) | May 31, 2023 USD ($) | Nov. 30, 2022 USD ($) | May 31, 2022 USD ($) | Jun. 30, 2020 USD ($) | Jun. 30, 2019 USD ($) | Dec. 31, 2024 USD ($) | Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) | Dec. 31, 2024 EUR (€) | Jun. 30, 2022 EUR (€) | Jun. 30, 2020 EUR (€) | Jun. 30, 2019 EUR (€)
Long-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) |  |  |  |  |  |  | 5.00% |  |  |  |  |  |  |  |  | 5.00% |  |  | 5.00% |  |  |
Lease payments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 77,362 | $ 45,472 |  |  |  |
Redemption price percentage |  |  |  | 101.094% | 101.094% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.40% |  |  |  |  |  |
Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | us-gaap:SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember |  |  |  |  |  |
Interest rate swap |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Face amount |  |  |  |  |  |  | $ 22,300 |  |  |  |  |  |  |  |  | $ 22,300 | 38,700 |  |  |  |  |
Net liability, prepaid expenses |  |  |  |  |  |  | 18,300 |  |  |  |  |  |  |  |  | 18,300 | 21,600 |  |  |  |  |
Net liability, other long term |  |  |  |  |  |  | 4,000 |  |  |  |  |  |  |  |  | 4,000 | 17,100 |  |  |  |  |
Unrealized gains (losses) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 23,400 | 23,400 |  |  |  |  |
Interest rate (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.50% |  |  |  |  |  |
Interest rate swap | Cash |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Margin deposits |  |  |  |  |  |  | 22,300 |  |  |  |  |  |  |  |  | $ 22,300 |  |  |  |  |  |
Interest rate swap | Unrestricted cash |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Margin deposits |  |  |  |  |  |  | 1,100 |  |  |  |  |  |  |  |  | 1,100 |  |  |  |  |  |
2027 Mirror Notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Face amount |  | $ 300,000 |  |  |  |  | 300,000 |  |  |  |  |  |  |  |  | $ 300,000 |  |  |  |  |  |
Proceeds from issuance of secured debt |  |  |  |  |  |  | $ 291,900 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of face value |  |  |  |  |  |  | 98.50% |  |  |  |  |  |  |  |  | 98.50% |  |  | 98.50% |  |  |
Lease payments |  |  |  |  |  |  | $ 114,600 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum percentage of principal amount entitled for redemption |  | 90.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
2027 Mirror Notes | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of principal amount considered as default debt |  | 25.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
2027 Mirror Notes | Redemption of some or all the notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Redemption price percentage of principal amount redeemed | 103.50% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
2027 Mirror Notes | If certain events have occurred |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repurchase price, percentage |  | 101.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
2027 Mirror Notes | If certain events have not occurred |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repurchase price in cash, percentage |  | 100.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
2027 Notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Face amount |  |  |  | $ 450,000 |  |  | $ 450,000 |  |  |  |  |  |  |  |  | $ 450,000 |  |  |  |  |  |
Interest rate (as a percent) |  |  |  | 7.00% |  |  | 7.00% |  |  |  |  |  |  |  |  | 7.00% |  |  | 7.00% |  |  |
Proceeds from issuance of secured debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 446,000 |  |  |  |  |  |
Debt costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,300 |  |  |  |  |  |
Discount on issuance of debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 2,700 |  |  |  |  |  |
2027 Notes | June 15, 2024 to June 14, 2025 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Redemption price percentage of principal amount redeemed |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 103.50% |  |  |  |  |  |
2026 Notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Face amount |  |  |  |  |  | $ 500,000 | $ 500,000 |  |  |  |  |  |  |  |  | $ 500,000 |  |  |  |  |  |
Interest rate (as a percent) |  |  |  |  |  |  | 3.50% |  |  |  |  |  |  |  |  | 3.50% |  |  | 3.50% |  |  |
Debt costs |  |  |  |  |  | 1,300 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Redemption price percentage of principal amount redeemed |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 100.00% |  |  |  |  |  |
Net proceeds |  |  |  |  |  | 496,900 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Discount on issuance of debt |  |  |  |  |  | $ 1,800 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Secured IPv4 notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Face amount |  |  | $ 206,000 |  |  |  | $ 206,000 |  |  |  |  |  |  |  |  | $ 206,000 |  |  |  |  |  |
Interest rate (as a percent) |  |  |  |  |  |  | 7.924% |  |  |  |  |  |  |  |  | 7.924% |  |  | 7.924% |  |  |
Proceeds from issuance of secured debt |  |  | $ 198,400 |  |  |  |  |  |  |  |  |  |  |  |  | $ 198,426 |  |  |  |  |  |
Debt costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 7,600 |  |  |  |  |  |
Maturity date |  |  | May 31, 2054 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Additional interest accrued on percentage of principal amount |  |  | 5.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Unsecured 2024 Notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Face amount | € |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | € 350.0 | € 350.0 | € 215.0 | € 135.0
Interest rate (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4.375% |
Redemption price percentage |  |  |  | 101.094% | 101.094% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net proceeds |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 240,300 | $ 152,100 |  |  |  |  |  |  |
Gain on foreign exchange |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 31,600 | 32,500 |  |  |  |
Aggregate principal amount of redemption | € |  |  |  |  | 350.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Redemption value |  |  |  | $ 375,200 | € 353.8 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of interest |  |  |  | 8,100 | 7.7 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total repayment |  |  |  | 383,400 | € 361.5 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss on extinguishment & redemption of 2022 notes |  |  |  | $ 11,900 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt fair value |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 365,800 | 397,000 |  |  |  |
2024 Notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4.375% |  |
Gain (loss) on foreign exchange |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 31,600 |  |  |  |
Installment One | Interest rate swap |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net proceeds |  |  |  |  |  |  |  |  |  |  |  |  | $ 2,100 |  |  |  |  |  |  |  |  |
Payment made to counter party |  |  |  |  |  |  |  |  | $ 24,200 |  |  |  |  |  |  |  |  |  |  |  |  |
Installment Two | Interest rate swap |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net proceeds |  |  |  |  |  |  |  | $ 24,200 |  | $ 21,500 |  | $ 2,100 |  |  |  |  |  |  |  |  |  |
Payment made to counter party |  |  |  |  |  |  |  |  |  |  | $ 21,500 |  |  |  |  |  |  |  |  |  |  |

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