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Long-term debt: (Details) - USD ($) $ in Thousands |  |  |  |  | 1 Months Ended | 3 Months Ended | 6 Months Ended |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Apr. 11, 2025 | Jun. 15, 2024 | Jun. 11, 2024 | May 02, 2024 | Nov. 30, 2024 | May 31, 2024 | Mar. 31, 2025 | Mar. 31, 2024 | Oct. 31, 2024 | Apr. 30, 2024 | Dec. 31, 2024
Long-term debt |  |  |  |  |  |  |  |  |  |  |
Lease payments |  |  |  |  |  |  | $ 8,003 | $ 23,235 |  |  |
Subsequent Events |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |
Proceeds from issuance of secured debt | $ 170,500 |  |  |  |  |  |  |  |  |  |
Interest rate swap |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |
Net liability |  |  |  |  |  |  | 22,500 |  |  |  | $ 22,300
Interest rate swap | Cash |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |
Margin deposits |  |  |  |  |  |  | 23,600 |  |  |  |
Interest rate swap | Restricted cash |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |
Margin deposits |  |  |  |  |  |  | 22,500 |  |  |  |
Interest rate swap | Unrestricted cash |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |
Margin deposits |  |  |  |  |  |  | 1,100 |  |  |  |
Interest rate swap | Accrued and other current liabilities |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |
Net liability |  |  |  |  |  |  | 18,600 |  |  |  | 18,300
Interest rate swap | Other long-term liabilities |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |
Net liability |  |  |  |  |  |  | $ 3,900 |  |  |  | $ 4,000
SOFR | Interest rate swap |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) |  |  |  |  |  |  | 3.50% |  |  |  |
Payment made to counter party |  |  |  |  |  | $ 12,100 |  |  |  |  |
Net proceeds |  |  |  |  |  |  |  |  | $ 12,100 | $ 12,100 |
Payment of debt in Installments |  |  |  |  | $ 12,100 |  |  |  |  |  |
2027 Mirror Notes |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |
Face amount |  |  | $ 300,000 |  |  |  | $ 300,000 |  |  |  |
Interest rate (as a percent) |  |  | 7.00% |  |  |  |  |  |  |  |
Percentage of face value |  |  |  |  |  |  | 98.50% |  |  |  |
Proceeds from issuance of secured debt |  |  |  |  |  |  | $ 291,900 |  |  |  |
Lease payments |  |  |  |  |  |  | 114,600 |  |  |  |
Maturity date |  |  | Jun. 15, 2027 |  |  |  |  |  |  |  |
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% |  |  |  |  |  |  |  |
Secured IPv4 Notes | Subsequent Events |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |
Face amount | $ 380,400 |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) | 6.646% |  |  |  |  |  |  |  |  |  |
IPv4 Notes |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |
Face amount |  |  |  | $ 206,000 |  |  | $ 206,000 |  |  |  |
Interest rate (as a percent) |  |  |  | 7.924% |  |  | 7.924% |  |  |  |
Proceeds from issuance of secured debt |  |  |  | $ 198,400 |  |  |  |  |  |  |
Maturity date |  |  |  | May 31, 2054 |  |  |  |  |  |  |
Additional interest accrued on percentage of principal amount |  |  |  | 5.00% |  |  |  |  |  |  |
IPv4 Notes | Base rate |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  |  |  |  |  |  | 5.00% |  |  |  |
IPv4 Notes | United States Treasury interest |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  |  |  |  |  |  | 3.40% |  |  |  |
Senior Unsecured Notes of 7.00 Due 2027 |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |
Face amount |  |  |  |  |  |  | $ 450,000 |  |  |  |
Interest rate (as a percent) |  |  |  |  |  |  | 7.00% |  |  |  |
New IPv4 Notes | Subsequent Events |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |
Face amount | $ 174,400 |  |  |  |  |  |  |  |  |  |
Maturity date | Apr. 30, 2055 |  |  |  |  |  |  |  |  |  |
Additional interest accrued on percentage of principal amount | 5.00% |  |  |  |  |  |  |  |  |  |
New IPv4 Notes | Base rate | Subsequent Events |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Basis Spread on Variable Rate | 5.00% |  |  |  |  |  |  |  |  |  |
New IPv4 Notes | United States Treasury interest | Subsequent Events |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Basis Spread on Variable Rate | 3.00% |  |  |  |  |  |  |  |  |  |

X
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