Intangible Assets (Indefinite-Lived Intangible Assets) (Details) $ in Millions	6 Months Ended
	Sep. 30, 2017 USD ($)
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets, Period Start	$ 40,585
Indefinite-lived Intangible Assets, Period End	41,072
Goodwill, beginning balance	6,579
Goodwill, Period Increase (Decrease)	(1)
Goodwill, ending balance	6,578
Total indefinite-lived intangible assets including FCC licenses, Trademarks, Goodwill, beginning balance	47,164
Indefinite lived intangible assets period increase decrease	486
Total indefinite-lived intangible assets including FCC licenses, Trademarks, Goodwill, ending balance	47,650
FCC Licenses [Member]
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets, Period Start	36,550
Indefinite-lived Intangible Assets, Period Increase (Decrease)	487
Indefinite-lived Intangible Assets, Period End	37,037
Trademarks [Member]
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets, Period Start	4,035
Indefinite-lived Intangible Assets, Period Increase (Decrease)	0
Indefinite-lived Intangible Assets, Period End	$ 4,035