Basis Of Presentation And Significant Accounting Policies - Disaggregated Revenue Parenthetical (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Operating revenues	[1]	$ 443,635	$ 439,910
Barter
Operating revenues		$ 7,000	$ 7,000

[1] (1)See Note 2 for the disclosures of operating revenues and operating loss included in discontinued operations for the historical periods.