Fair Value Of Financial Instruments (Schedule Of Impact On Carrying Value Of Cell C Investment) (Details) $ in Thousands	Jun. 30, 2020 USD ($)
3.0% Increase [Member] | Weighted Average Cost of Capital (WACC) Rate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Sensitivity for fair value of Cell C investment	$ 0
3.0% Increase [Member] | EBITDA Multiple [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Sensitivity for fair value of Cell C investment	2,528
2.0% Decrease [Member] | Weighted Average Cost of Capital (WACC) Rate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Sensitivity for fair value of Cell C investment	1,680
2.0% Decrease [Member] | EBITDA Multiple [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Sensitivity for fair value of Cell C investment	$ 0