Supplemental Financial Information (Details) - USD ($) $ in Millions	Mar. 31, 2019	Apr. 01, 2018	Mar. 31, 2018
Accounts and notes receivable, net
Trade	$ 3,024		$ 2,916
Unbilled trade and other	893		1,204
Less allowance for doubtful accounts	(363)		(409)
Accounts and notes receivable, net	3,554		3,711
Prepaid expenses and other current assets
Prepaid expenses	278		263
Deferred charges and other	321		312
Prepaid expense and other assets, current	1,289	$ 846	575
Other assets
Unbilled trade installment receivables, net	247		154
Investments	60		197
Restricted Cash, Noncurrent	81		49
Other	492		521
Other assets	1,118	964	921
Accounts payable
Trade	3,462		3,068
Accrued interconnection costs	90		80
Capital expenditures and other	409		261
Accounts payable	3,961		3,409
Accrued expenses and other current liabilities
Deferred revenues	288		1,454
Accrued interest	359		423
Accrued taxes	301		410
Payroll and related	555		405
Accrued legal reserves	180		194
Severance, lease and other exit costs	50		108
Asset Retirement Obligation, Current	44		145
Unfavorable lease liabilities	137		152
Other	721		671
Accrued expenses and other current liabilites	3,597	3,927	3,962
Other liabilities
Deferred rental income-communications towers	187		199
Deferred rent	631		605
Asset retirement obligations	622		486
Unfavorable lease liabilities	200		337
Post-retirement benefits and other non-current employee related liabilities	789		833
Deferred spectrum lease liability	486		416
Contract with Customer, Liability, Current	47
Other liabilities	475		607
Other liabilities	3,437	$ 3,451	3,483
Checks issued in excess of associated bank balances but not yet presented for collection	75		$ 66
Prepaid Expenses and Other Current Assets [Member]
Prepaid expenses and other current assets
Contract with Customer, Asset, Net, Current	690
Other Assets [Member]
Prepaid expenses and other current assets
Contract with Customer, Asset, Net, Current	$ 238