Segments (Operating Revenues by Service and Products) (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	Mar. 31, 2013	Jul. 10, 2013	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2013
Segment Reporting Information [Line Items]
Inter-segment revenues		$ 8,071	$ 8,107	$ 7,975	$ 8,027	$ 8,292	$ 8,973	$ 8,488	$ 8,789
Successor [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues										$ 8,875	$ 0		$ 32,180	$ 34,532	$ 16,891
Net operating revenues										8,875	0	$ 16,891	32,180	34,532	16,891
Successor [Member] | Services [Member]
Segment Reporting Information [Line Items]
Net operating revenues										7,096			24,627	26,544	13,579
Successor [Member] | Equipment [Member]
Segment Reporting Information [Line Items]
Net operating revenues										999		1,797	5,006	4,990
Successor [Member] | Voice [Member]
Segment Reporting Information [Line Items]
Net operating revenues										264		479	511	809
Successor [Member] | Data [Member]
Segment Reporting Information [Line Items]
Net operating revenues										36		69	102	125
Successor [Member] | Internet [Member]
Segment Reporting Information [Line Items]
Net operating revenues										308		666	1,094	1,188
Successor [Member] | Other Products or Services [Member]
Segment Reporting Information [Line Items]
Net operating revenues										172		301	840	876
Successor [Member] | Wireless [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues										8,254			30,377	32,327	15,642
Net operating revenues										8,254	0		30,377	32,327	15,642
Successor [Member] | Wireless [Member] | Services [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues										7,096			24,627	26,544	13,579
Successor [Member] | Wireless [Member] | Equipment [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues										999			5,006	4,990	1,797
Successor [Member] | Wireless [Member] | Voice [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues										0			0	0	0
Successor [Member] | Wireless [Member] | Data [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues										0			0	0	0
Successor [Member] | Wireless [Member] | Internet [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues										0			0	0	0
Successor [Member] | Wireless [Member] | Other Products or Services [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues										159			744	793	266
Successor [Member] | Wireline [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues										770		1,636	2,382	2,814
Net operating revenues										617	0		1,790	2,191	1,240
Successor [Member] | Wireline [Member] | Services [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues										0			0	0	0
Successor [Member] | Wireline [Member] | Equipment [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues										0		0	0	0
Successor [Member] | Wireline [Member] | Voice [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues										352		719	840	1,174
Successor [Member] | Wireline [Member] | Data [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues										62		138	171	213
Successor [Member] | Wireline [Member] | Internet [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues										345		747	1,284	1,353
Successor [Member] | Wireline [Member] | Other Products or Services [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues										11		32	87	74
Successor [Member] | Corporate, Other And Eliminations [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[1]									(149)		(387)	(579)	(609)
Net operating revenues										4	0		13	14	9
Successor [Member] | Corporate, Other And Eliminations [Member] | Services [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[1]									0			0	0	$ 0
Successor [Member] | Corporate, Other And Eliminations [Member] | Equipment [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[1]									0		0	0	0
Successor [Member] | Corporate, Other And Eliminations [Member] | Voice [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[1]									(88)		(240)	(329)	(365)
Successor [Member] | Corporate, Other And Eliminations [Member] | Data [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[1]									(26)		(69)	(69)	(88)
Successor [Member] | Corporate, Other And Eliminations [Member] | Internet [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[1]									(37)		(81)	(190)	(165)
Successor [Member] | Corporate, Other And Eliminations [Member] | Other Products or Services [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[1]									$ 2		3	$ 9	$ 9
Predecessor [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues											8,793	18,602
Net operating revenues											8,793	18,602
Predecessor [Member] | Services [Member]
Segment Reporting Information [Line Items]
Net operating revenues											7,143	15,139
Predecessor [Member] | Equipment [Member]
Segment Reporting Information [Line Items]
Net operating revenues											813	1,707
Predecessor [Member] | Voice [Member]
Segment Reporting Information [Line Items]
Net operating revenues											253	535
Predecessor [Member] | Data [Member]
Segment Reporting Information [Line Items]
Net operating revenues											48	95
Predecessor [Member] | Internet [Member]
Segment Reporting Information [Line Items]
Net operating revenues											387	813
Predecessor [Member] | Other Products or Services [Member]
Segment Reporting Information [Line Items]
Net operating revenues											149	313
Predecessor [Member] | Wireless [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues											8,089	17,125
Net operating revenues											8,089	17,125
Predecessor [Member] | Wireless [Member] | Services [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues											7,143	15,139
Predecessor [Member] | Wireless [Member] | Equipment [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues											813	1,707
Predecessor [Member] | Wireless [Member] | Voice [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues											0	0
Predecessor [Member] | Wireless [Member] | Data [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues											0	0
Predecessor [Member] | Wireless [Member] | Internet [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues											0	0
Predecessor [Member] | Wireless [Member] | Other Products or Services [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues											133	279
Predecessor [Member] | Wireline [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues											893	1,901
Net operating revenues											702	1,471
Predecessor [Member] | Wireline [Member] | Services [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues											0	0
Predecessor [Member] | Wireline [Member] | Equipment [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues											0	0
Predecessor [Member] | Wireline [Member] | Voice [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues											352	771
Predecessor [Member] | Wireline [Member] | Data [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues											94	188
Predecessor [Member] | Wireline [Member] | Internet [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues											434	913
Predecessor [Member] | Wireline [Member] | Other Products or Services [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues											13	29
Predecessor [Member] | Corporate, Other And Eliminations [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[1]										(189)	(424)
Net operating revenues											2	6
Predecessor [Member] | Corporate, Other And Eliminations [Member] | Services [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[1]										0	0
Predecessor [Member] | Corporate, Other And Eliminations [Member] | Equipment [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[1]										0	0
Predecessor [Member] | Corporate, Other And Eliminations [Member] | Voice [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[1]										(99)	(236)
Predecessor [Member] | Corporate, Other And Eliminations [Member] | Data [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[1]										(46)	(93)
Predecessor [Member] | Corporate, Other And Eliminations [Member] | Internet [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[1]										(47)	(100)
Predecessor [Member] | Corporate, Other And Eliminations [Member] | Other Products or Services [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	[1]										$ 3	$ 5

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