Fair Value Of Financial Instruments (Schedule Of Key Valuation Inputs Used To Measure Fair Value Of Investment In Cell C) (Details) $ in Millions, R in Billions	12 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 ZAR (R)	Jun. 30, 2019 ZAR (R)
Deferred tax including assessed tax losses	$ 167.3	$ 205.9	R 2.9	R 2.9
Weighted Average Cost of Capital (WACC) Rate [Member] | Minimum [Member]
Investment fair value measurement inputs	15.00%
Weighted Average Cost of Capital (WACC) Rate [Member] | Maximum [Member]
Investment fair value measurement inputs	21.00%
Cell C [Member]
Net adjusted external debt	$ 900.0	$ 1,000.0	15.8	13.9
Lease liabilities included in net adjusted external debt			R 4.4	R 6.4
Cell C [Member] | Long Term Growth Rate [Member] | Minimum [Member]
Investment fair value measurement inputs		3.00%
Cell C [Member] | Long Term Growth Rate [Member] | Maximum [Member]
Investment fair value measurement inputs		4.50%
Cell C [Member] | Marketability Discount [Member]
Investment fair value measurement inputs	10.00%
Cell C [Member] | Minority Discount [Member]
Investment fair value measurement inputs	15.00%