Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Change in interest rate swaps, tax	$ 2	$ 4	$ 0	$ 11

Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives During Period Before Tax Adjustment, Tax

No definition available.

Name:	avya_OtherComprehensiveIncomeLossUnrealizedGainLossonDerivativesDuringPeriodBeforeTaxAdjustmentTax
Namespace Prefix:	avya_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration