Acquisitions - Additional Information (Detail) - USD ($) $ in Thousands					3 Months Ended								12 Months Ended
	Jun. 11, 2018	Jan. 16, 2018	Nov. 01, 2017	Apr. 04, 2017	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Total net revenue					$ 82,073	$ 74,575	$ 74,329	$ 66,838	$ 73,460	$ 334,555	$ 70,509	$ 57,510	$ 297,815	$ 536,034	$ 258,514
Expenses													264,238	258,173	209,658
Payment for relocation of television station											$ 32,600
Smadex
Business Acquisition [Line Items]
Business acquisition date	Jun. 11, 2018
Ownership Interest acquired	100.00%
Aggregate cash consideration	$ 3,500
Cash acquired	1,200
Accounts receivables assets acquired, fair value	900
Gross amount account receivables asset acquired	$ 900
Total net revenue													6,400
Expenses													5,800
Acquisition fees and costs													400
Headway
Business Acquisition [Line Items]
Business acquisition date				Apr. 04, 2017
Ownership Interest acquired				100.00%
Aggregate cash consideration				$ 8,200
Cash acquired				4,500
Accounts receivables assets acquired, fair value				19,800
Gross amount account receivables asset acquired				20,900
Acquisition fees and costs														500	$ 800
Fair value of contingent consideration				$ 15,900	$ 7,800				$ 15,900				$ 7,800	$ 15,900
Contingent consideration agreement, payment period				3 years
Contingent consideration arrangements, minimum				$ 0
Contingent consideration arrangements, maximum				27,000
Amount due under contract expected to be uncollectible				1,100
Headway | Maximum
Business Acquisition [Line Items]
Contingent consideration, payments				$ 7,500
KMCC-TV
Business Acquisition [Line Items]
Business acquisition date		Jan. 16, 2018
Aggregate cash consideration		$ 3,600
Business acquisition description of acquired entity													the Company completed the acquisition of television station KMCC-TV, which serves the Las Vegas, Nevada area
KMIR-TV and KPSE-LD
Business Acquisition [Line Items]
Business acquisition date			Nov. 01, 2017
Aggregate cash consideration			$ 21,000
Business acquisition description of acquired entity			the Company completed the acquisition of television stations KMIR-TV, the local NBC affiliate, and KPSE-LD, the local MyNetworkTV affiliate, both of which serve the Palm Springs, California area