Financing Arrangements (Narrative) (Details) - USD ($) $ in Millions		9 Months Ended
	May 29, 2015	Jun. 30, 2016	Jun. 30, 2015	Sep. 30, 2015	Jun. 05, 2015	Mar. 31, 2015
Debt Instrument [Line Items]
Repayments of Long-term Debt		$ 19	$ 25
Long-term Debt, Gross		$ 6,061
Debt, Weighted Average Interest Rate		7.30%		7.30%
Proceeds from sale-leaseback transactions		$ 14	15
Secured Debt | Senior Secured Multi-Currency Asset-Based Revolver
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity		200				$ 150
Letters of Credit Outstanding, Amount		116		$ 119
Long-term Debt		60		55
Proceeds from Domestic ABL		203	0
Secured Debt | Senior Secured Multi-Currency Asset-Based Revolver | Base Rate Borrowings
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		335
Secured Debt | Letter of Credit
Debt Instrument [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity		37		83
Secured Debt | Senior Secured Term B-3 Loans
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		24		22
Proceeds from Domestic ABL		48	20
Line of Credit Facility, Remaining Borrowing Capacity		15		101
Secured Debt | Senior Secured Term B-3 Loans | Base Rate Borrowings
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		150
Secured Debt | Senior Secured Multi-Currency Revolver
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity					$ 18	$ 200
Proceeds from Domestic ABL		17	50
Secured Debt | Senior secured term B-4 loans
Debt Instrument [Line Items]
Proceeds from Issuance of Long-term Debt	$ 2,125	0	$ 2,100
Repayments of Long-term Debt		19
Other current liabilities
Debt Instrument [Line Items]
Capital lease obligations		63		61
Avaya Pivate Cloud Services business | Other current liabilities
Debt Instrument [Line Items]
Capital lease obligations		49		48
Principal Amount
Debt Instrument [Line Items]
Long-term Debt		6,061		6,042
Principal Amount | Variable rate senior secured multi-currency revolver
Debt Instrument [Line Items]
Debt Instrument, Fair Value Disclosure		17		18
Principal Amount | Secured Debt | Senior Secured Multi-Currency Asset-Based Revolver
Debt Instrument [Line Items]
Long-term Debt		60		55
Principal Amount | Secured Debt | Senior Secured Term B-3 Loans
Debt Instrument [Line Items]
Long-term Debt		53		20
Principal Amount | Secured Debt | Senior Secured Multi-Currency Revolver
Debt Instrument [Line Items]
Long-term Debt		17		18
Principal Amount | Secured Debt | Senior secured term B-4 loans
Debt Instrument [Line Items]
Long-term Debt		2,094		2,112
Principal Amount | Secured Debt | Senior Secured Term B-6 Loans
Debt Instrument [Line Items]
Long-term Debt		537		537
Principal Amount | Secured Debt | 9% Senior secured notes
Debt Instrument [Line Items]
Long-term Debt		290		290
Principal Amount | Secured Debt | Senior secured notes
Debt Instrument [Line Items]
Long-term Debt		1,009		1,009
Principal Amount | Secured Debt | 10.50% Senior secured notes
Debt Instrument [Line Items]
Long-term Debt		1,384		1,384
Principal Amount | Secured Debt | Senior Secured Term B-3 and B-4 Loans [Member]
Debt Instrument [Line Items]
Long-term Debt		617
Net of Discounts and Issuance Costs
Debt Instrument [Line Items]
Long-term Debt		5,999		5,967
Net of Discounts and Issuance Costs | Secured Debt | Senior Secured Multi-Currency Asset-Based Revolver
Debt Instrument [Line Items]
Long-term Debt		60		55
Net of Discounts and Issuance Costs | Secured Debt | Senior Secured Term B-3 Loans
Debt Instrument [Line Items]
Long-term Debt		53		20
Net of Discounts and Issuance Costs | Secured Debt | Senior Secured Multi-Currency Revolver
Debt Instrument [Line Items]
Long-term Debt		17		18
Net of Discounts and Issuance Costs | Secured Debt | Senior secured term B-4 loans
Debt Instrument [Line Items]
Long-term Debt		2,064		2,077
Net of Discounts and Issuance Costs | Secured Debt | Senior Secured Term B-6 Loans
Debt Instrument [Line Items]
Long-term Debt		534		532
Net of Discounts and Issuance Costs | Secured Debt | 9% Senior secured notes
Debt Instrument [Line Items]
Long-term Debt		287		286
Net of Discounts and Issuance Costs | Secured Debt | Senior secured notes
Debt Instrument [Line Items]
Long-term Debt		1,001		999
Net of Discounts and Issuance Costs | Secured Debt | 10.50% Senior secured notes
Debt Instrument [Line Items]
Long-term Debt		$ 1,370		$ 1,368