Equity-Accounted Investments And Other Long-Term Assets (Summary Of Unrealized Gain (Loss) On Investments) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jun. 30, 2017
Schedule Of Equity And Held To Maturity Investments [Line Items]
Cost basis	$ 178,127
Unrealized holding gains	38,612
Unrealized holding losses
Carrying value	216,739	$ 0
Cell C [Member]
Schedule Of Equity And Held To Maturity Investments [Line Items]
Cost basis	169,127
Unrealized holding gains	37,843
Unrealized holding losses
Carrying value	206,970
Cedar Cellular [Member]
Schedule Of Equity And Held To Maturity Investments [Line Items]
Cost basis	9,000
Unrealized holding gains	769
Unrealized holding losses
Carrying value	$ 9,769