Organization and Business Operations (Details) Viewer in Millions	Dec. 31, 2017 Viewer TelevisionStation Market
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of full power television stations owned, operated, programmed or provided sales and other services	170
Number of markets in which the Company's stations broadcast | Market	100
Approximate number of viewers | Viewer	43.6
Approximate number of viewers (in hundredths)	38.90%
Number of full power television stations owned or operated by independent third parties	36