Segments (Operating Revenues by Service and Products) (Details) - USD ($) $ in Millions		3 Months Ended
		Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Net operating revenues		$ 8,027	$ 8,789
Segment Reporting Information, Total Net Operating Revenues		8,027	8,789
Services [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information, Total Net Operating Revenues		6,351	6,908
Equipment [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information, Total Net Operating Revenues		990	1,106
Voice [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information, Total Net Operating Revenues		151	236
Data [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information, Total Net Operating Revenues		29	32
Internet [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information, Total Net Operating Revenues		284	307
Other Products or Services [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information, Total Net Operating Revenues		222	200
Wireless [Member]
Segment Reporting Information [Line Items]
Net operating revenues		7,540	8,193
Segment Reporting Information, Total Net Operating Revenues		7,540	8,193
Wireless [Member] | Services [Member]
Segment Reporting Information [Line Items]
Net operating revenues		6,351	6,908
Wireless [Member] | Equipment [Member]
Segment Reporting Information [Line Items]
Net operating revenues		990	1,106
Wireless [Member] | Voice [Member]
Segment Reporting Information [Line Items]
Net operating revenues		0	0
Wireless [Member] | Data [Member]
Segment Reporting Information [Line Items]
Net operating revenues		0	0
Wireless [Member] | Internet [Member]
Segment Reporting Information [Line Items]
Net operating revenues		0	0
Wireless [Member] | Other Products or Services [Member]
Segment Reporting Information [Line Items]
Net operating revenues		199	179
Wireline [Member]
Segment Reporting Information [Line Items]
Net operating revenues		630	746
Segment Reporting Information, Total Net Operating Revenues		483	593
Wireline [Member] | Services [Member]
Segment Reporting Information [Line Items]
Net operating revenues		0	0
Wireline [Member] | Equipment [Member]
Segment Reporting Information [Line Items]
Net operating revenues		0	0
Wireline [Member] | Voice [Member]
Segment Reporting Information [Line Items]
Net operating revenues		233	327
Wireline [Member] | Data [Member]
Segment Reporting Information [Line Items]
Net operating revenues		49	56
Wireline [Member] | Internet [Member]
Segment Reporting Information [Line Items]
Net operating revenues		328	345
Wireline [Member] | Other Products or Services [Member]
Segment Reporting Information [Line Items]
Net operating revenues		20	18
Corporate, Other And Eliminations [Member]
Segment Reporting Information [Line Items]
Net operating revenues	[1]	(143)	(150)
Segment Reporting Information, Total Net Operating Revenues		4	3
Corporate, Other And Eliminations [Member] | Services [Member]
Segment Reporting Information [Line Items]
Net operating revenues		0	0
Corporate, Other And Eliminations [Member] | Equipment [Member]
Segment Reporting Information [Line Items]
Net operating revenues		0	0
Corporate, Other And Eliminations [Member] | Voice [Member]
Segment Reporting Information [Line Items]
Net operating revenues		(82)	(91)
Corporate, Other And Eliminations [Member] | Data [Member]
Segment Reporting Information [Line Items]
Net operating revenues		(20)	(24)
Corporate, Other And Eliminations [Member] | Internet [Member]
Segment Reporting Information [Line Items]
Net operating revenues		(44)	(38)
Corporate, Other And Eliminations [Member] | Other Products or Services [Member]
Segment Reporting Information [Line Items]
Net operating revenues		$ 3	$ 3

[1] Revenues eliminated in consolidation consist primarily of wireline services provided to the Wireless segment for resale to or use by wireless subscribers.