Goodwill and Intangible Assets - Goodwill Rollforward (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2025	Dec. 31, 2024
Goodwill [Line Items]
Goodwill, accumulated impairment losses	$ 2,405	$ 2,405
Goodwill [Roll Forward]
As of December 31, 2024	6,955
Reclassified as held for sale	(1,305)
As of September 30, 2025	5,650
Lumen Mass Markets fiber-to-the-home business | Held-for-sale
Goodwill [Line Items]
Goodwill	$ 1,305