Supplemental Financial Information (Details) - USD ($) $ in Millions		Mar. 31, 2016	Sep. 30, 2015	Mar. 31, 2015
Accounts and notes receivable, net
Trade		$ 899		$ 1,037
Unbilled trade and other		239		1,457
Less allowance for doubtful accounts		(39)		(204)
Accounts and notes receivable, net		1,099		2,290
Prepaid expenses and other current assets
Prepaid expenses		366		401
Trading Securities, Other		1,155		1,198
Deferred charges and other		399		291
Prepaid expense and other assets, current		1,920		1,890
Receivable from Conduits		116	$ 1,500	0
Other assets
Unbilled trade installment receivables, net		0		361
Investments		187		151
Other		425		376
Other assets		728		888
Accounts payable
Trade	[1]	2,567		3,786
Accrued interconnection costs	[1]	142		198
Capital expenditures and other	[1]	190		363
Accounts payable	[1]	2,899		4,347
Accrued expenses and other current liabilities
Deferred revenues		1,456		1,385
Accrued taxes		232		238
Payroll and related		339		589
Severance, lease and other exit costs		288		223
Accrued interest		532		525
Accrued capital expenditures		149		705
Other		1,378		1,628
Accrued expenses and other current liabilites		4,374		5,293
Other liabilities
Deferred rental income-communications towers		218		229
Deferred rent		478		366
Asset retirement obligations		550		584
Unfavorable lease liabilities		658		856
Post-retirement benefits and other non-current employee related liabilities		994		987
Other		1,104		929
Other liabilities		4,002		3,951
Successor [Member]
Prepaid expenses and other current assets
Prepaid expense and other assets, current		1,920		1,890
Other assets
Other assets		728		888
Accounts payable
Accounts payable		2,899		4,347
Accrued expenses and other current liabilities
Accrued expenses and other current liabilites		4,374		5,293
Other liabilities
Other liabilities		4,002		3,951
Checks issued in excess of associated bank balances but not yet presented for collection		$ 66		$ 90

[1] Includes liabilities in the amounts of $66 million and $90 million as of March 31, 2016 and 2015, respectively, for checks issued in excess of associated bank balances but not yet presented for collection.