Fair Value Of Financial Instruments (Narrative) (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Fair Value Of Financial Instruments [Abstract]
Reclassifications of investments between Level 1, 2, or 3	$ 0	$ 0
Liabilities Subject To Compromise Debt	$ 10,949,000,000

Fair Value, Equity, Between Levels One, Two Or Three, Amount

No definition available.

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Namespace Prefix:	ftr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant