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Acquisitions and Dispositions - Additional Information (Detail) - USD ($)							3 Months Ended			9 Months Ended
	Sep. 27, 2018	Mar. 15, 2018	Dec. 19, 2017	May 01, 2017	Jan. 06, 2017	Nov. 01, 2016	Sep. 30, 2018	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Feb. 27, 2017
Business Acquisition [Line Items]
Adjustment of operating loss carryforwards recognized in Income tax expense							$ 200,000			$ 200,000
Proceeds from sale assets held for sale				$ 11,000,000	$ 24,000,000
Loss on dispositions, net									$ 300,000		$ 3,707,993
Translator license and equipment received as consideration				$ 300,000							$ 332,000
Asset purchase agreement, cash purchase price										39,520,000
Goodwill deductible for tax							$ 10,100,000			10,100,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Business Acquisition [Line Items]
Gain on disposition								$ 4,000,000
Greater Media Inc. [Member]
Business Acquisition [Line Items]
Merger agreement date						Nov. 01, 2016
Business acquisition, sales price						$ 28,000,000							$ 28,000,000
Business acquisition, number of shares expected to be returned						650,759
Business acquisition fair value of shares returned		$ 4,800,000				$ 3,400,000						$ 6,300,000
Estimate of net operating loss carry forwards										$ 3,600,000
Greater Media Inc. [Member] \| Treasury Stock [Member]
Business Acquisition [Line Items]
Business acquisition, number of shares expected to be returned		470,480
Greater Media Inc. [Member] \| Shares Released from Escrow [Member]
Business Acquisition [Line Items]
Fair value of shares forfeited in escrow		$ 8,800,000										$ 11,600,000
Greater Media Inc. [Member] \| Shares Released from Escrow [Member] \| Treasury Stock [Member]
Business Acquisition [Line Items]
Business acquisition, number of shares expected to be forfeited and recorded in treasury stock		867,679
Greater Media Inc. [Member] \| Class A Common Stock [Member] \| Common Stock to be Held in Escrow [Member]
Business Acquisition [Line Items]
Number of shares issuable upon acquisition						867,679
Value of shares issuable upon acquisition						$ 4,200,000
Greater Media Inc. [Member] \| Class A Common Stock [Member] \| Shares Released from Escrow [Member]
Business Acquisition [Line Items]
Number of shares issuable upon acquisition						189,915
Value of shares issuable upon acquisition						$ 900,000
Fair value of shares forfeited in escrow						$ 3,300,000
CBS Radio Stations Inc., Entercom Boston LLC and The Entercom Divestiture Trust [Member]
Business Acquisition [Line Items]
Asset purchase agreement, cash purchase price			$ 12,000,000
Business acquisition partially financed by borrowings			6,000,000
Business acquisition partially funded in cash			$ 6,000,000
WXTU-FM [Member]
Business Acquisition [Line Items]
Merger agreement date	Sep. 27, 2018
Asset purchase agreement, cash purchase price	$ 38,000,000
Business acquisition partially financed by borrowings	35,000,000
Business acquisition partially funded in cash	3,000,000
Business acquisition,transaction expenses	$ 100,000