Guarantor Financial Information (CONDENSED CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (LOSS)) (Details) - USD ($) $ in Millions	3 Months Ended											6 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Jul. 09, 2013	Mar. 31, 2013	Jul. 10, 2013	Mar. 31, 2016	Mar. 31, 2015		Dec. 31, 2013
Condensed Income Statements, Captions [Line Items]
Revenues	$ 8,071	$ 8,107	$ 7,975	$ 8,027	$ 8,292	$ 8,973	$ 8,488	$ 8,789
Net operating expenses:
Depreciation													$ 1,800	$ 206
Operating income (loss)	8	(197)	(2)	501	318	(2,540)	(192)	519
Other (expense) income:
Income tax benefit (expense)												$ (1,600)
Net (loss) income	$ (554)	$ (836)	$ (585)	$ (20)	$ (224)	$ (2,379)	$ (765)	$ 23
Asset impairments													166
Successor [Member]
Condensed Income Statements, Captions [Line Items]
Service									$ 7,876		$ 0		27,174	29,542		$ 15,094
Equipment									999		0		5,006	4,990		1,797
Revenues									8,875		0		32,180	34,532		16,891
Cost of services (exclusive of depreciation and amortization below)									2,622		0		9,439	9,660		5,174
Cost of products (exclusive of depreciation and amortization below)									2,038		0		5,795	9,309		4,603
Net operating expenses:
Selling, general and administrative									2,371		14		8,479	9,563		4,841
Severance, exit costs and asset impairments									52				409	304
Depreciation									868		0		5,794	3,797		2,026
Amortization									429		0		1,294	1,552		908
Total costs and expenses									8,455		14		31,870	36,427		17,861
Operating income (loss)									420		(14)		310	(1,895)		(970)
Other (expense) income:
Interest and Other Income									4				11	12		35
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
(Losses) earnings of subsidiaries									0				0	0		0
Other nonoperating income (expense), excluding interest income									(3)				7	15		38
Nonoperating income (expense)									(515)		6		(2,164)	(2,024)		(845)
Income (loss) before income taxes									(95)		(8)		(1,854)	(3,919)		(1,815)
Income tax benefit (expense)									(56)		(1)		(141)	574		(45)
Net (loss) income									(151)		(9)		(1,995)	(3,345)		(1,860)
Other comprehensive (loss) income									(145)		0		(31)	(365)		102
Comprehensive (loss)									(296)		(9)		(2,026)	(3,710)		(1,758)
Asset impairments									0		0		0	2,133	[1]	0
Severance and exit costs									52		0		409	304		309
Other income (expense), net									1		6		18	27		73
Other, net									75		0		660	109		0
Successor [Member] | Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Service									0				0	0		0
Equipment									0				0	0		0
Revenues									0				0	0		0
Cost of services (exclusive of depreciation and amortization below)									0				0	0		0
Cost of products (exclusive of depreciation and amortization below)									0				0	0		0
Net operating expenses:
Selling, general and administrative									0				0	0		0
Depreciation									0				0	0		0
Amortization									0				0	0		0
Total costs and expenses									0				0	1		0
Operating income (loss)									0				0	(1)		0
Other (expense) income:
Interest and Other Income									20				165	146		40
Interest Expense									(373)				(1,624)	(1,521)		(548)
(Losses) earnings of subsidiaries									199				(538)	(1,970)		(1,320)
Other nonoperating income (expense), excluding interest income									0				0	1		(3)
Nonoperating income (expense)									(154)				(1,997)	(3,344)		(1,831)
Income (loss) before income taxes									(154)				(1,997)	(3,345)		(1,831)
Income tax benefit (expense)									0				0	0		0
Net (loss) income									(154)				(1,997)	(3,345)		(1,831)
Other comprehensive (loss) income									(145)				(31)	(365)		102
Comprehensive (loss)									(299)				(2,028)	(3,710)		(1,729)
Asset impairments														0
Severance and exit costs									0				0	0		0
Other, net									0				0	1
Successor [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Service									7,876				27,174	29,542		15,094
Equipment									999				5,006	4,990		1,797
Revenues									8,875				32,180	34,532		16,891
Cost of services (exclusive of depreciation and amortization below)									2,622				9,439	9,660		5,174
Cost of products (exclusive of depreciation and amortization below)									2,038				5,795	9,309		4,603
Net operating expenses:
Selling, general and administrative									2,371				8,479	9,563		4,805
Depreciation									868				5,794	3,797		2,026
Amortization									429				1,294	1,552		908
Total costs and expenses									8,455				31,870	36,426		17,825
Operating income (loss)									420				310	(1,894)		(934)
Other (expense) income:
Interest and Other Income									4				5	3		6
Interest Expense									(166)				(717)	(667)		(407)
(Losses) earnings of subsidiaries									0				0	0		0
Other nonoperating income (expense), excluding interest income									(3)				7	14		56
Nonoperating income (expense)									(165)				(705)	(650)		(345)
Income (loss) before income taxes									255				(395)	(2,544)		(1,279)
Income tax benefit (expense)									(56)				(143)	574		(41)
Net (loss) income									199				(538)	(1,970)		(1,320)
Other comprehensive (loss) income									(147)				(21)	(355)		93
Comprehensive (loss)									52				(559)	(2,325)		(1,227)
Asset impairments														2,133
Severance and exit costs									52				409	304		309
Other, net									75				660	108
Successor [Member] | Consolidation, Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Service									0				0	0		0
Equipment									0				0	0		0
Revenues									0				0	0		0
Cost of services (exclusive of depreciation and amortization below)									0				0	0		0
Cost of products (exclusive of depreciation and amortization below)									0				0	0		0
Net operating expenses:
Selling, general and administrative									0				0	0		0
Depreciation									0				0	0		0
Amortization									0				0	0		0
Total costs and expenses									0				0	0		0
Operating income (loss)									0				0	0		0
Other (expense) income:
Interest and Other Income									(189)				(949)	(824)		(200)
Interest Expense									189				949	824		200
(Losses) earnings of subsidiaries									(45)				2,535	5,315		3,151
Other nonoperating income (expense), excluding interest income									0				0	0		0
Nonoperating income (expense)									(45)				2,535	5,315		3,151
Income (loss) before income taxes									(45)				2,535	5,315		3,151
Income tax benefit (expense)									0				0	0		0
Net (loss) income									(45)				2,535	5,315		3,151
Other comprehensive (loss) income									292				52	720		(195)
Comprehensive (loss)									247				2,587	6,035		2,956
Asset impairments														0
Severance and exit costs									0				0	0		0
Other, net									0				0	0
Successor [Member] | Parent [Member]
Condensed Income Statements, Captions [Line Items]
Service									0				0	0		0
Equipment									0				0	0		0
Revenues									0				0	0		0
Cost of services (exclusive of depreciation and amortization below)									0				0	0		0
Cost of products (exclusive of depreciation and amortization below)									0				0	0		0
Net operating expenses:
Selling, general and administrative									0				0	0		36
Depreciation									0				0	0		0
Amortization									0				0	0		0
Total costs and expenses									0				0	0		36
Operating income (loss)									0				0	0		(36)
Other (expense) income:
Interest and Other Income									169				790	687		189
Interest Expense									(166)				(790)	(687)		(163)
(Losses) earnings of subsidiaries									(154)				(1,997)	(3,345)		(1,831)
Other nonoperating income (expense), excluding interest income									0				0	0		(15)
Nonoperating income (expense)									(151)				(1,997)	(3,345)		(1,820)
Income (loss) before income taxes									(151)				(1,997)	(3,345)		(1,856)
Income tax benefit (expense)									0				2	0		(4)
Net (loss) income									(151)				(1,995)	(3,345)		(1,860)
Other comprehensive (loss) income									(145)				(31)	(365)		102
Comprehensive (loss)									(296)				(2,026)	(3,710)		(1,758)
Asset impairments														0
Severance and exit costs									0				0	0		$ 0
Other, net									$ 0				$ 0	$ 0
Predecessor [Member]
Condensed Income Statements, Captions [Line Items]
Service											7,980	16,895
Equipment											813	1,707
Revenues											8,793	18,602
Cost of services (exclusive of depreciation and amortization below)											2,640	5,673
Cost of products (exclusive of depreciation and amortization below)											2,293	4,872
Net operating expenses:
Selling, general and administrative											2,336	5,067
Severance, exit costs and asset impairments											25
Depreciation											1,422	3,098
Amortization											70	147
Total costs and expenses											8,764	19,487
Operating income (loss)											29	(885)
Other (expense) income:
Interest and Other Income											14	33
Interest Expense											(432)	(1,135)
Equity in losses of unconsolidated investments, net										$ (482)	(202)	(482)
Gain on previously-held equity interests											0	2,926
(Losses) earnings of subsidiaries											0	0
Other nonoperating income (expense), excluding interest income											(14)	(14)
Nonoperating income (expense)											(634)	1,328
Income (loss) before income taxes											(605)	443
Income tax benefit (expense)											(38)	(1,601)
Net (loss) income											(643)	(1,158)
Other comprehensive (loss) income											14	23
Comprehensive (loss)											(629)	(1,135)
Asset impairments											0	0
Severance and exit costs											25	652
Other income (expense), net											0	19
Other, net											(22)	(22)
Predecessor [Member] | Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Service											0	0
Equipment											0	0
Revenues											0	0
Cost of services (exclusive of depreciation and amortization below)											0	0
Cost of products (exclusive of depreciation and amortization below)											0	0
Net operating expenses:
Selling, general and administrative											0	0
Depreciation											0	0
Amortization											0	0
Total costs and expenses											0	0
Operating income (loss)											0	0
Other (expense) income:
Interest and Other Income											29	61
Interest Expense											(292)	(842)
Equity in losses of unconsolidated investments, net											0	0
Gain on previously-held equity interests												0
(Losses) earnings of subsidiaries											(368)	(365)
Other nonoperating income (expense), excluding interest income											(12)	(12)
Nonoperating income (expense)											(643)	(1,158)
Income (loss) before income taxes											(643)	(1,158)
Income tax benefit (expense)											0	0
Net (loss) income											(643)	(1,158)
Other comprehensive (loss) income											14	23
Comprehensive (loss)											(629)	(1,135)
Severance and exit costs											0	0
Other, net											0	0
Predecessor [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Service											7,980	16,895
Equipment											813	1,707
Revenues											8,793	18,602
Cost of services (exclusive of depreciation and amortization below)											2,640	5,673
Cost of products (exclusive of depreciation and amortization below)											2,293	4,872
Net operating expenses:
Selling, general and administrative											2,336	5,067
Depreciation											1,422	3,098
Amortization											70	147
Total costs and expenses											8,764	19,487
Operating income (loss)											29	(885)
Other (expense) income:
Interest and Other Income											6	15
Interest Expense											(161)	(336)
Equity in losses of unconsolidated investments, net											(202)	(482)
Gain on previously-held equity interests												2,926
(Losses) earnings of subsidiaries											0	0
Other nonoperating income (expense), excluding interest income											(2)	(2)
Nonoperating income (expense)											(359)	2,121
Income (loss) before income taxes											(330)	1,236
Income tax benefit (expense)											(38)	(1,601)
Net (loss) income											(368)	(365)
Other comprehensive (loss) income											15	35
Comprehensive (loss)											(353)	(330)
Severance and exit costs											25	652
Other, net											(22)	(22)
Predecessor [Member] | Consolidation, Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Service											0	0
Equipment											0	0
Revenues											0	0
Cost of services (exclusive of depreciation and amortization below)											0	0
Cost of products (exclusive of depreciation and amortization below)											0	0
Net operating expenses:
Selling, general and administrative											0	0
Depreciation											0	0
Amortization											0	0
Total costs and expenses											0	0
Operating income (loss)											0	0
Other (expense) income:
Interest and Other Income											(21)	(43)
Interest Expense											21	43
Equity in losses of unconsolidated investments, net											0	0
Gain on previously-held equity interests												0
(Losses) earnings of subsidiaries											368	365
Other nonoperating income (expense), excluding interest income											0	0
Nonoperating income (expense)											368	365
Income (loss) before income taxes											368	365
Income tax benefit (expense)											0	0
Net (loss) income											368	365
Other comprehensive (loss) income											(15)	(35)
Comprehensive (loss)											353	330
Severance and exit costs											0	0
Other, net											$ 0	$ 0

[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.