Supplemental Financial Information (Details) - USD ($) $ in Millions		Mar. 31, 2017	Mar. 31, 2016
Accounts and notes receivable, net
Trade		$ 2,947	$ 899
Unbilled trade and other		1,545	239
Less allowance for doubtful accounts		(354)	(39)
Accounts and notes receivable, net		4,138	1,099
Prepaid expenses and other current assets
Prepaid expenses		298	366
Trading Securities, Other		0	1,155
Deferred charges and other		303	399
Prepaid expense and other assets, current		601	1,920
Receivable from Conduits		0	116
Other assets
Unbilled trade installment receivables, net		569	0
Investments		237	187
Other		507	425
Other assets		1,313	728
Accounts payable
Trade	[1]	2,937	2,567
Accrued interconnection costs	[1]	123	142
Capital expenditures and other	[1]	221	190
Accounts payable	[1]	3,281	2,899
Accrued expenses and other current liabilities
Deferred revenues		1,445	1,456
Accrued taxes		435	232
Payroll and related		339	339
Severance, lease and other exit costs		83	288
Accrued interest		511	532
Other		1,328	1,527
Accrued expenses and other current liabilites		4,141	4,374
Other liabilities
Deferred rental income-communications towers		207	218
Deferred rent		554	478
Asset retirement obligations		462	550
Unfavorable lease liabilities		490	658
Post-retirement benefits and other non-current employee related liabilities		861	994
Other		989	1,104
Other liabilities		3,563	4,002
Checks issued in excess of associated bank balances but not yet presented for collection		$ 69	$ 66

[1] Includes liabilities in the amounts of $69 million and $66 million as of March 31, 2017 and 2016, respectively, for payments issued in excess of associated bank balances but not yet presented for collection.