Equity-Accounted Investments And Other Long-Term Assets (Summary Of Contractual Maturity Of Investment) (Details) $ in Thousands	Sep. 30, 2018 USD ($)
Equity-Accounted Investments And Other Long-Term Assets [Abstract]
Due in one year or less, Cost basis
Due in one year through five years, Cost basis	9,000
Due in five years through ten years, Cost basis
Due after ten years, Cost basis
Total, Cost basis	9,000
Due in one year or less, Estimated fair value		[1]
Due in one year through five years, Estimated fair value	9,625	[1]
Due in five years through ten years, Estimated fair value		[1]
Due after ten years, Estimated fair value		[1]
Total, Estimated fair value	$ 9,625	[1]

[1] The estimated fair value of the Cedar Cellular note has been calculated utilizing the Company's portion of the security provided to the Company by Cedar Cellular, namely, Cedar Cellular's investment in Cell C.