Intangible Assets (Indefinite-Lived Intangible Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Indefinite-lived Intangible Assets [Line Items]
FCC licenses and trademarks, beginning balance	$ 40,585
FCC licenses and trademarks, ending balance	41,309	$ 40,585
Goodwill, beginning balance	6,579	6,575
Goodwill, Period Increase (Decrease)	7	4
Goodwill, ending balance	6,586	6,579
Total indefinite-lived intangible assets including FCC licenses, Trademarks, Goodwill, beginning balance	47,164	46,648
Indefinite lived intangible assets period increase decrease	731	516
Total indefinite-lived intangible assets including FCC licenses, Trademarks, Goodwill, ending balance	47,895	47,164
FCC Licenses [Member]
Indefinite-lived Intangible Assets [Line Items]
FCC licenses and trademarks, beginning balance	36,550	36,038
FCC licenses and trademarks, period increase (decrease)	724	512
FCC licenses and trademarks, ending balance	37,274	36,550
Trademarks [Member]
Indefinite-lived Intangible Assets [Line Items]
FCC licenses and trademarks, beginning balance	4,035	4,035
FCC licenses and trademarks, period increase (decrease)		0
Impairment of intangible assets, indefinite-lived (excluding goodwill)	0
FCC licenses and trademarks, ending balance	4,035	4,035
Other, Net [Member]
Indefinite-lived Intangible Assets [Line Items]
Gain (Loss) on Disposition of Intangible Assets	479	$ 354
Corporate Joint Venture [Member] | FCC Licenses [Member]
Indefinite-lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	$ 150