Basis Of Presentation And Significant Accounting Policies - Disaggregated Revenue Parenthetical (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating revenues	[1]	$ 498,008	$ 450,533	$ 1,431,001	$ 1,359,960
Barter
Operating revenues		$ 7,000	$ 7,000	$ 21,000	$ 21,000

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