Acquisitions, Disposals and Other Transactions (Fiscal 2018) (Narrative) (Details) $ in Millions	1 Months Ended		9 Months Ended		12 Months Ended	21 Months Ended
	Jul. 31, 2017 USD ($)	Mar. 31, 2017 TelevisionStation	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2019 USD ($)
Disposals
Proceeds received from the FCC's completed reverse auction for broadcast spectrum			$ 0	$ 354
Television Broadcast Station Spectrum
Disposals
Proceeds received from the FCC's completed reverse auction for broadcast spectrum	$ 354
Number of television stations with bids to relinquish spectrum accepted by the FCC as part of the auction | TelevisionStation		3
Pre-tax gain on disposals					$ 102	$ 114