Segments (Segment Financial Information) (Details) $ in Millions		3 Months Ended		6 Months Ended
		Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) segments	Sep. 30, 2014 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments | segments				2
Segment Reporting Information, Total Net Operating Revenues		$ 7,975	$ 8,488	$ 16,002	$ 17,277
Revenues		7,975	8,488	16,002	17,277
Segment Operating Expenses		(5,967)	(7,102)	(11,912)	(14,064)
Segment Reporting Information Operating Income or Loss		2,008	1,386	4,090	3,213
Depreciation		1,412	898	2,653	1,766
Amortization		(331)	(396)	(678)	(809)
Impairments		85	0	85	0
Other Operating Expenses Net	[1]	182	284	175	311
Operating Income		(2)	(192)	499	327
Interest Expense		(542)	(510)	(1,084)	(1,022)
Other income, net		5	8	9	9
Loss (income) before income taxes		(539)	(694)	(576)	(686)
Payments to Acquire Property, Plant and Equipment Inclusive of Equipment on Lease				4,081
Capital Expenditures - network and others				2,964	2,389
Severance and exit costs		25	284	38	311
Restructuring Charges			(284)	(18)	(311)
Wireless [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information, Total Net Operating Revenues		7,516	7,929	15,056	16,122
Revenues		7,516	7,929	15,056	16,122
Segment Operating Expenses		(5,537)	(6,559)	(11,003)	(12,959)
Segment Reporting Information Operating Income or Loss		1,979	1,370	4,053	3,163
Payments to Acquire Property, Plant and Equipment Inclusive of Equipment on Lease				3,759
Capital Expenditures - network and others					2,109
Wireline [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information, Total Net Operating Revenues		455	555	938	1,148
Revenues		609	708	1,239	1,454
Segment Operating Expenses		(580)	(681)	(1,201)	(1,392)
Segment Reporting Information Operating Income or Loss		29	27	38	62
Payments to Acquire Property, Plant and Equipment Inclusive of Equipment on Lease				131
Capital Expenditures - network and others					124
Corporate, Other And Eliminations [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information, Total Net Operating Revenues		4	4	8	7
Revenues	[2]	(150)	(149)	(293)	(299)
Segment Operating Expenses		150	138	292	287
Segment Reporting Information Operating Income or Loss		0	(11)	(1)	(12)
Payments to Acquire Property, Plant and Equipment Inclusive of Equipment on Lease				191
Capital Expenditures - network and others					156
Lease and severance [Member]
Segment Reporting Information [Line Items]
Severance and exit costs		25		38
Lease [Member]
Segment Reporting Information [Line Items]
Restructuring Charges	[3]			2
Lease [Member] | Wireless [Member]
Segment Reporting Information [Line Items]
Restructuring Charges	[4]	(13)		(18)
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	[5]	0	0	0	0
Intersegment Eliminations [Member] | Wireless [Member]
Segment Reporting Information [Line Items]
Revenues		0	0	0	0
Intersegment Eliminations [Member] | Wireline [Member]
Segment Reporting Information [Line Items]
Revenues		154	153	301	306
Intersegment Eliminations [Member] | Corporate, Other And Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		$ (154)	$ (153)	(301)	$ (306)
Other Operating Income (Expense) [Member] | Wireless [Member]
Segment Reporting Information [Line Items]
Restructuring Reserve, Accrual Adjustment				$ 20

[1] Other, net for the three and six-month periods ended September 30, 2015 consists of $25 million and $38 million, respectively, of severance and exit costs as well as a $157 million accrual for ongoing legal matters recognized in the three-month period ended September 30, 2015. In addition, the six-month period ended September 30, 2015 includes a $20 million release of liability reserves associated with the May 2013 U.S. Cellular asset acquisition. Other, net for the three and six-month periods ended September 30, 2014 consists of $284 million and $311 million, respectively, of severance and exit costs

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

[3] In addition to the $20 million income (Wireless only) related to U.S. Cellular, we recognized costs of $13 million (Wireless only), and $18 million (Wireless only) for the three and six-month periods ended September 30, 2015, respectively, included in "Other, net" on the consolidated statements of comprehensive loss.

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

[5] Inter-segment revenues consist primarily of wireline services provided to the Wireless segment for resale to, or use by, wireless subscribers.