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Income taxes - Effective income tax rate reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Reconciliation of the Federal statutory income taxes to the amounts reported in the financial statements
Federal income tax expense at statutory rates	$ 54,381	$ (256,086)	$ (5,537)
State income taxes, net of federal benefit	1,587	3,722	(1,700)
Impact of foreign operations	(1,602)	868	(651)
Non-deductible expenses	(2,713)	(2,783)	(2,679)
Bargain purchase gain - Sprint Business acquisition	4,662	295,351
Tax effect of TCJA from foreign earnings		(490)	(360)
Changes in valuation allowance	(740)	13,382	(10,303)
Income tax benefit (expense)	$ 55,575	$ 53,964	$ (21,230)

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