Investment And Other Income, Net (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Investment And Other Income, Net [Abstract]
Special termination benefit enhancements related to a voluntary separation plan, pension plan	$ 45
OPEB remeasurement gain (loss)	35	$ (3)	$ 248
Pension remeasurement (loss) gain	$ (45)	$ 202	$ 218

Special Termination Benefit Enhancements, Pension Plan Remeasurement

No definition available.

Name:	fybr_SpecialTerminationBenefitEnhancementsPensionPlanRemeasurement
Namespace Prefix:	fybr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration