Quarterly report pursuant to Section 13 or 15(d)

Acquisitions and Recent Transactions - Summary of Business Acquisitions and Asset Purchased (Detail)

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Acquisitions and Recent Transactions - Summary of Business Acquisitions and Asset Purchased (Detail) - USD ($)
 9 Months Ended
Apr. 19, 2018
Sep. 30, 2018
Acquisition Date [Line Items]    
Business Combination, Consideration Transferred   $ 11,180,000
KTRB-AM, San Francisco, California (Asset Purchase) [Member]    
Acquisition Date [Line Items]    
Business Combination, Consideration Transferred   $ 5,349,000
Business Acquisition, Effective Date of Acquisition   Sep. 11, 2018
Hilary Kramer Financial Newsletter (Business Acquisition) [Member]    
Acquisition Date [Line Items]    
Business Combination, Consideration Transferred   $ 439,000
Business Acquisition, Effective Date of Acquisition   Aug. 09, 2018
Just1Word (Business Acquisition) [Member]    
Acquisition Date [Line Items]    
Business Combination, Consideration Transferred   $ 312,000
Business Acquisition, Effective Date of Acquisition   Aug. 07, 2018
KZTS-AM (formerly KDXE-AM), Little Rock, Arkansas (asset purchase) [Member]    
Acquisition Date [Line Items]    
Business Combination, Consideration Transferred   $ 210,000
Business Acquisition, Effective Date of Acquisition   Jul. 25, 2018
Childrens-Ministry-Deals.com (Business Acquisition) [Member]    
Acquisition Date [Line Items]    
Business Combination, Consideration Transferred   $ 3,700,000
Business Acquisition, Effective Date of Acquisition   Jul. 24, 2018
KDXE-FM (Formerly KZTS-FM), Little Rock, Arkansas (Business Acquisition) [Member]    
Acquisition Date [Line Items]    
Business Combination, Consideration Transferred   $ 1,100,000
Business Acquisition, Effective Date of Acquisition   Jun. 25, 2018
HearItFirst.com (Asset Purchase) [Member]    
Acquisition Date [Line Items]    
Business Combination, Consideration Transferred $ 70,000 $ 70,000
Business Acquisition, Effective Date of Acquisition   Apr. 19, 2018