Severance and Exit Costs (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	$ 11		$ 18
Restructuring Charges			$ 284	18	$ 311
Lease and access exit costs [Member] | Minimum [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring And Related Cost Expected Future Cost				100
Lease and access exit costs [Member] | Maximum [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring And Related Cost Expected Future Cost				225
Wireless [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		10
Other Operating Income (Expense) [Member] | Wireless [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	$ 16
Restructuring Reserve, Accrual Adjustment				$ 20

[1] For the three and six-month periods ended September 30, 2015, we recognized costs of $11 million ($10 million Wireless, $1 million Wireline), and $18 million ($16 million Wireless, $2 million Wireline), respectively, included in "Other, net" on the consolidated statements of comprehensive loss.