Intangible Assets (Indefinite-Lived Intangible Assets) (Details) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
		Mar. 31, 2015	Jun. 30, 2014	Mar. 31, 2016		Mar. 31, 2015
Indefinite-lived Intangible Assets [Line Items]
FCC licenses and trademarks, beginning balance				$ 39,987
FCC licenses and trademarks, ending balance		$ 39,987		40,073		$ 39,987
Goodwill, beginning balance				6,575
Goodwill, ending balance		6,575		6,575		6,575
Successor [Member]
Indefinite-lived Intangible Assets [Line Items]
FCC licenses and trademarks, beginning balance				39,987
FCC licenses and trademarks, ending balance		39,987		40,073		39,987
Goodwill, beginning balance			$ 6,383	6,575		6,383
Goodwill, period increase (decrease)		232	40	0	[1]	192
Goodwill, ending balance		6,575		6,575		6,575
Total indefinite-lived intangible assets including FCC licenses, Trademarks, Goodwill, beginning balance			48,361	46,562		48,361
Indefinite lived intangible assets period increase decrease				86		(1,799)
Total indefinite-lived intangible assets including FCC licenses, Trademarks, Goodwill, ending balance		46,562		46,648		46,562
Successor [Member] | FCC Licenses [Member]
Indefinite-lived Intangible Assets [Line Items]
FCC licenses and trademarks, beginning balance			36,043	35,952		36,043
FCC licenses and trademarks, period increase (decrease)				86		(91)
FCC licenses and trademarks, ending balance		35,952		36,038		35,952
Successor [Member] | Trademarks [Member]
Indefinite-lived Intangible Assets [Line Items]
FCC licenses and trademarks, beginning balance			$ 5,935	4,035		5,935
FCC licenses and trademarks, period increase (decrease)						(1,900)
Impairment of intangible assets, indefinite-lived (excluding goodwill)	[2]			0
FCC licenses and trademarks, ending balance		$ 4,035		$ 4,035		$ 4,035

[1] Net additions to goodwill for the Successor year ended March 31, 2015 of approximately $192 million were the result of purchase price allocation adjustments, which consisted of a $232 million increase recorded during the three-month period ended March 31, 2015 to correct the amount of net deferred tax liabilities recognized in connection with the SoftBank Merger and Clearwire Acquisition and a net $40 million decrease recorded during the three-months ended June 30, 2014, which is also associated with the SoftBank Merger and Clearwire Acquisition.

[2] 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.