Background - Change in Accounting Estimates and Correction of Immaterial Errors (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2024	Jan. 01, 2024	Dec. 31, 2023	Jan. 01, 2023
Change in Accounting Estimate [Line Items]
Retained earnings	$ 1,802	$ 1,802		$ 706
Fiber Network Assets
Change in Accounting Estimate [Line Items]
Property, Plant and Equipment, Useful Life			30 years	25 years
Fiber Network Assets | Change in Accounting Method Accounted for as Change in Estimate
Change in Accounting Estimate [Line Items]
Depreciation	(6)	(18)
Depreciation, Net Of Tax	(4)	(13)
Competitive Local Exchange Carriers Fixed Assets | Change in Accounting Method Accounted for as Change in Estimate
Change in Accounting Estimate [Line Items]
Depreciation	(30)	(78)
Depreciation, Net Of Tax	$ (23)	$ (59)
Correction Of Error From Understatement Of Revenues And Network Expenses Prior To 2021
Change in Accounting Estimate [Line Items]
Retained earnings					$ 13