Intangible Assets (Indefinite-Lived Intangible Assets) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Sep. 30, 2014
Indefinite-lived Intangible Assets [Line Items]
Total indefinite-lived intangible assets including FCC licenses, Trademarks, Goodwill, beginning balance	$ 48,361
Indefinite lived intangible assets period increase decrease	(218)
Total indefinite-lived intangible assets including FCC licenses, Trademarks, Goodwill, ending balance	48,143
Successor [Member]
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets, Period Start	41,978
Indefinite-lived Intangible Assets, Period End	41,800
Goodwill, beginning balance	6,383
Goodwill, Period Increase (Decrease)	(40)	[1]
Goodwill, ending balance	6,343
Successor [Member] | FCC Licenses [Member]
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets, Period Start	36,043
Indefinite-lived Intangible Assets, Period Increase (Decrease)	(178)
Indefinite-lived Intangible Assets, Period End	35,865
Successor [Member] | Trademarks [Member]
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets, Period Start	5,935
Indefinite-lived Intangible Assets, Period Increase (Decrease)	0
Indefinite-lived Intangible Assets, Period End	$ 5,935

[1] Net reduction to goodwill for the Successor six-month period ended September 30, 2014 of approximately $40 million was the result of purchase price allocation adjustments, which consisted of a $44 million decrease associated with the SoftBank Merger and a $4 million increase associated with the Clearwire Acquisition.