Intangible Assets (Indefinite-Lived Intangible Assets) (Details) $ in Millions	9 Months Ended
	Dec. 31, 2017 USD ($)
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets, Period Start	$ 40,585
Indefinite-lived Intangible Assets, Period End	41,222
Goodwill, beginning balance	6,579
Goodwill, Period Increase (Decrease)	7
Goodwill, ending balance	6,586
Total indefinite-lived intangible assets including FCC licenses, Trademarks, Goodwill, beginning balance	47,164
Indefinite lived intangible assets period increase decrease	644
Total indefinite-lived intangible assets including FCC licenses, Trademarks, Goodwill, ending balance	47,808
FCC Licenses [Member]
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets, Period Start	36,550
Indefinite-lived Intangible Assets, Period Increase (Decrease)	637
Indefinite-lived Intangible Assets, Period End	37,187
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
Corporate Joint Venture [Member] | FCC Licenses [Member]
Indefinite-lived Intangible Assets [Line Items]
Intangible assets acquired	$ 150