Other Financial Information - Current Liabilities (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2025	Dec. 31, 2024
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Current affiliate obligation	$ 48	$ 48
Current operating lease liability	14	15
Legal reserves	47	1
Other	43	53
Total Other current liabilities	152	117
Capital expenditures	36	$ 57
Held-for-sale | Lumen Mass Markets fiber-to-the-home business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other current liabilities	$ 2