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Description of the business and summary of significant accounting policies: - Financial instruments (Details) - USD ($) $ in Millions	Dec. 31, 2024	May 02, 2024	Dec. 31, 2023	May 07, 2021
Description of the business:
Interest rate (as a percent)	5.00%
Interest rate swap
Description of the business:
Face amount	$ 22.3		$ 38.7
Level 2 \| Interest rate swap
Description of the business:
long-term liability	22.3
Senior unsecured 2027 Notes \| Level 2
Description of the business:
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Interest rate (as a percent)	7.00%
Senior notes, fair value	$ 450.0
Senior Unsecured Mirror Notes due 2027 \| Level 2
Description of the business:
Senior notes	$ 300.0
Interest rate (as a percent)	7.00%
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Senior secured 2026 Notes
Description of the business:
Interest rate (as a percent)	3.50%
Face amount	$ 500.0			$ 500.0
Senior secured 2026 Notes \| Level 2
Description of the business:
Senior notes	$ 500.0
Interest rate (as a percent)	3.50%
Senior notes, fair value	$ 482.5
Secured IPv4 notes
Description of the business:
Interest rate (as a percent)	7.924%
Face amount	$ 206.0	$ 206.0
Secured IPv4 Notes \| Level 2
Description of the business:
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Senior notes, fair value	$ 211.8