Segments (Segment Financial Information) (Details) $ in Millions		3 Months Ended											6 Months Ended		12 Months Ended					15 Months Ended
		Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Jul. 09, 2013 USD ($)	Mar. 31, 2013 USD ($)	Dec. 31, 2013 USD ($)	Jul. 10, 2013 USD ($)	Mar. 31, 2016 USD ($) segments		Mar. 31, 2015 USD ($)		Dec. 31, 2013 USD ($)	Mar. 31, 2014 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segments															2
Inter-segment revenues		$ 8,071	$ 8,107	$ 7,975	$ 8,027	$ 8,292	$ 8,973	$ 8,488	$ 8,789
Depreciation															$ (1,800)		$ (206)
Impairments															(166)
Operating (loss) income		8	(197)	$ (2)	$ 501	318	(2,540)	$ (192)	$ 519
Assets		78,975				82,841									78,975		82,841
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property															487
Gain (Loss) on Disposition of Property Plant Equipment			$ 65
Successor [Member]
Segment Reporting Information [Line Items]
Net operating revenues										$ 8,875		$ 0		$ 16,891	32,180		34,532		$ 16,891
Inter-segment revenues										8,875		0			32,180		34,532		16,891
Total segment operating expenses										(7,031)		(14)			(24,034)		(28,532)		(14,525)
Segment earnings										1,844		(14)			8,146		6,000		2,366
Depreciation										(868)		0			(5,794)		(3,797)		(2,026)
Amortization										(429)		0			(1,294)		(1,552)		(908)
Impairments										0		0			0		(2,133)	[1]	0
Other, net	[2]									(127)					(748)		(413)		(402)
Operating (loss) income										420		(14)			310		(1,895)		(970)
Interest expense										(516)		0			(2,182)		(2,051)		(918)
Equity in losses of unconsolidated investments, net										0		0			0		0		0
Gain on previously-held equity interests										0		0			0		0		0
Other income (expense), net										1		6			18		27		73
Income (loss) before income taxes										(95)		(8)			(1,854)		(3,919)		(1,815)
Capital expenditures - network and other										1,488		0			4,680		5,422		3,847	$ 1,488
Capital expenditures - network and other, inclusive of equipment on lease															6,972		6,004
Assets		78,975				82,841				84,549		3,122	$ 85,953		78,975		82,841		85,953	84,549
Severance, exit costs and asset impairments										(52)					(409)		(304)
Legal fees										0		0			(193)		(91)		0
Pension expense																	59
Severance and exit costs										52		0			409		304		309
Business combination, acquisition related costs																			(100)
Other nonrecurring (income) expense													7
Restructuring charges															(391)		(263)
Other, net										(75)		0			(660)		(109)		0
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property										(75)
Successor [Member] | Corporate Segment [Member]
Segment Reporting Information [Line Items]
Business combination, acquisition related costs																			(75)
Successor [Member] | Wireless [Member]
Segment Reporting Information [Line Items]
Net operating revenues										8,254		0			30,377		32,327		15,642
Inter-segment revenues										8,254					30,377		32,327		15,642
Total segment operating expenses										(6,417)		0			(22,326)		(26,433)		(13,464)
Segment earnings										1,837		0			8,051		5,894		2,178
Capital expenditures - network and other															6,381		5,442		3,535	1,343
Assets		73,408				75,533				75,044		0	75,121		73,408		75,533		75,121	75,044
Business combination, acquisition related costs																			(25)
Successor [Member] | Wireline [Member]
Segment Reporting Information [Line Items]
Net operating revenues										617		0			1,790		2,191		1,240
Inter-segment revenues										770				1,636	2,382		2,814
Total segment operating expenses										(758)		0			(2,290)		(2,701)		(1,414)
Segment earnings										12		0			92		113		222
Capital expenditures - network and other															279		275		153	79
Assets		1,255				1,262				1,499		0	1,548		1,255		1,262		1,548	1,499
Impairment loss							233
Successor [Member] | Corporate, Other And Eliminations [Member]
Segment Reporting Information [Line Items]
Net operating revenues										4		0			13		14		9
Inter-segment revenues	[3]									(149)				(387)	(579)		(609)
Total segment operating expenses										144		(14)			582		602		353
Segment earnings										(5)		(14)			3		(7)		(34)
Capital expenditures - network and other															312		287		159	66
Assets		$ 4,312				$ 6,046				8,006		3,122	$ 9,284		4,312		6,046		9,284	$ 8,006
Successor [Member] | Lease [Member]
Segment Reporting Information [Line Items]
Restructuring charges															(156)	[4]	28	[5]
Successor [Member] | Lease [Member] | Wireless [Member]
Segment Reporting Information [Line Items]
Restructuring charges																	(12)
Successor [Member] | Lease [Member] | Wireline [Member]
Segment Reporting Information [Line Items]
Restructuring charges																	(1)
Predecessor [Member]
Segment Reporting Information [Line Items]
Net operating revenues												8,793		18,602
Inter-segment revenues												8,793		18,602
Total segment operating expenses												(7,269)		(15,559)
Segment earnings												1,524		3,043
Depreciation												(1,422)		(3,098)
Amortization												(70)		(147)
Impairments												0		0
Other, net	[2]											(3)		(683)
Operating (loss) income												29		(885)
Interest expense												(432)		(1,135)
Equity in losses of unconsolidated investments, net											$ (482)	(202)		(482)
Gain on previously-held equity interests												0		2,926
Income loss from equity method investments, net												(202)		2,444
Other income (expense), net												0		19
Income (loss) before income taxes												(605)		443
Capital expenditures - network and other												1,381		3,140
Severance, exit costs and asset impairments												(25)
Legal fees												0		0
Severance and exit costs												25		652
Business combination, acquisition related costs														(53)
Other, net												22		22
Predecessor [Member] | Wireless [Member]
Segment Reporting Information [Line Items]
Net operating revenues												8,089		17,125
Inter-segment revenues												8,089		17,125
Total segment operating expenses												(6,694)		(14,355)
Segment earnings												1,395		2,770
Capital expenditures - network and other												1,270		2,840
Predecessor [Member] | Wireline [Member]
Segment Reporting Information [Line Items]
Net operating revenues												702		1,471
Inter-segment revenues												893		1,901
Total segment operating expenses												(765)		(1,629)
Segment earnings												128		272
Capital expenditures - network and other												64		174
Predecessor [Member] | Corporate, Other And Eliminations [Member]
Segment Reporting Information [Line Items]
Net operating revenues												2		6
Inter-segment revenues	[3]											(189)		(424)
Total segment operating expenses												190		425
Segment earnings												1		1
Capital expenditures - network and other												47		126
Intersegment Eliminations [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[6]									0		0			0		0		0
Intersegment Eliminations [Member] | Successor [Member] | Wireless [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[6]									0		0			0		0		0
Intersegment Eliminations [Member] | Successor [Member] | Wireline [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[6]									153		0			592		623		396
Intersegment Eliminations [Member] | Successor [Member] | Corporate, Other And Eliminations [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[6]									$ (153)		0			(592)		$ (623)		$ (396)
Intersegment Eliminations [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[6]											0		0
Intersegment Eliminations [Member] | Predecessor [Member] | Wireless [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[6]											0		0
Intersegment Eliminations [Member] | Predecessor [Member] | Wireline [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[6]											191		430
Intersegment Eliminations [Member] | Predecessor [Member] | Corporate, Other And Eliminations [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[6]											$ (191)		$ (430)
Trademarks [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Impairment of intangible assets, indefinite-lived (excluding goodwill)	[7]														0
Trademarks [Member] | Successor [Member] | Wireless [Member]
Segment Reporting Information [Line Items]
Impairment of intangible assets, indefinite-lived (excluding goodwill)							$ 1,900
Leased devices [Member]
Segment Reporting Information [Line Items]
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property															256
Gain (Loss) on Disposition of Property Plant Equipment															65
Leased devices [Member] | Wireless [Member]
Segment Reporting Information [Line Items]
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property															$ 321

[1] (2)Impairments for the Successor year ended March 31, 2015 consist of a $1.9 billion trade name impairment related to the Wireless segment and a $233 million impairment related to Wireline long-lived assets.

[2] (3)Other, net for the Successor year ended March 31, 2016 consists of $409 million of severance and exit costs, combined with $193 million for legal reserves related to various pending legal suits and proceedings and a $166 million loss on disposal of property, plant and equipment related to cell site construction costs and other network costs that are no longer recoverable as a result of changes in the Company's network plans, partially offset by $20 million of income resulting from a revision to our estimate of a previously recorded reserve. Losses totaling approximately $321 million relating to the write-off of leased devices associated with lease cancellations of $256 million and the loss on sale of devices to MLS under the Handset Sale-Leaseback Tranche 1 transaction for $65 million were excluded from Other, net and included within Wireless segment earnings. Other, net for the Successor year ended March 31, 2015 consists of $304 million of severance and exit costs, combined with $91 million for legal reserves related to various pending legal suits and proceedings and $59 million for a partial pension settlement, partially offset by $41 million of income resulting from a revision to our estimate of a previously recorded reserve. Other, net for the Successor three-month transition period ended March 31, 2014 consists of $52 million of severance and exit costs and a $75 million loss on disposal of property, plant and equipment related to network equipment assets no longer necessary for management's strategic plans. Other, net for the Successor year ended December 31, 2013 consists of $309 million of severance and exit costs and $100 million of business combination fees paid to unrelated parties in connection with the transactions with SoftBank and Clearwire ($75 million included in our corporate segment and $25 million included in our wireless segment and classified as selling, general and administrative expenses), partially offset by $7 million of insurance reimbursement towards 2012 hurricane-related charges (included in our wireless segment and classified as a contra-expense in cost of services expense). Other, net for the Predecessor 191-day period ended July 10, 2013 and unaudited three-month period ended March 31, 2013 consists of $652 million and $25 million, respectively, of severance and exit costs, partially offset by $22 million of favorable developments in connection with an E911 regulatory tax-related contingency. Other, net for the Predecessor 191-day period ended July 10, 2013 also includes $53 million of business combination fees paid to unrelated parties in connection with the transactions with SoftBank and Clearwire (included in our corporate segment and classified as selling, general and administrative expenses).

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

[4] (1)We recognized costs of $176 million (Wireless only) for the Successor year ended March 31, 2016, which were offset by $20 million of income (Wireless only) resulting from a revision to our estimate of a previously recorded reserve.

[5] (4)We recognized costs of $13 million ($12 million Wireless and $1 million Wireline) for the year ended March 31, 2015, which were offset by $41 million of income (Wireless only) resulting from a revision to our estimate of a previously recorded reserve.

[6] (1)Inter-segment revenues consist primarily of wireline services provided to the Wireless segment for resale to or use by wireless subscribers.

[7] Net reduction to trademarks for the year ended March 31, 2015 of approximately $1.9 billion was related to the impairment of the Sprint trade name. See discussion below.