Intangible Assets (Indefinite-Lived Intangible Assets) (Details) $ in Millions	6 Months Ended
	Sep. 30, 2018 USD ($)
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets, Period Start	$ 41,309
Indefinite-lived Intangible Assets, Period End	41,373
Goodwill, beginning balance	6,586
Goodwill, Period Increase (Decrease)	12
Goodwill, ending balance	6,598
Total indefinite-lived intangible assets including FCC licenses, Trademarks, Goodwill, beginning balance	47,895
Indefinite lived intangible assets period increase decrease	76
Total indefinite-lived intangible assets including FCC licenses, Trademarks, Goodwill, ending balance	47,971
FCC Licenses [Member]
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets, Period Start	37,274
Indefinite-lived Intangible Assets, Period Increase (Decrease)	64
Indefinite-lived Intangible Assets, Period End	37,338
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