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Business acquisition equity interest forfeited number of shares.

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Business acquisition equity interest returned number of shares.

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Business acquisition fair value of shares forfeited.

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Business acquisition fair value of shares returned.

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Estimated net operating loss carry forwards.

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Date when the acquirer obtains control of the acquiree, in CCYY-MM-DD format.

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Value of equity interests (such as common shares, preferred shares, or partnership interest) issued or issuable to acquire the entity.

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Number of shares of equity interests issued or issuable to acquire entity.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of liabilities incurred by the acquirer as part of consideration transferred in a business combination.

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Amount before tax of gain (loss) recognized on the sale or disposal of a disposal group. Excludes discontinued operations.

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Amount of gain (loss) on sale or disposal of property, plant and equipment assets, excluding oil and gas property and timber property.

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The cash inflow associated with the amount received from the sale of a portion of the company's business, for example a segment, division, branch or other business, during the period.

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Acquisitions and Dispositions - Additional Information (Detail) - USD ($)						3 Months Ended
	Mar. 15, 2018	Dec. 19, 2017	May 01, 2017	Jan. 06, 2017	Nov. 01, 2016	Mar. 31, 2018	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2017	Feb. 27, 2017
Business Acquisition [Line Items]
Proceeds from sale assets held for sale			$ 11,000,000	$ 24,000,000
Loss on dispositions, net								$ (269,456)
Translator license and equipment received as consideration			$ 300,000
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]
Payment for exchange of radio station		$ 12,000,000
Business acquisition partially financed by borrowings		6,000,000
Business acquisition partially funded in cash		$ 6,000,000