Quarterly report pursuant to Section 13 or 15(d)

Broadcast Licenses - Schedule of Changes in Broadcasting Licenses (Detail)

v3.10.0.1
Broadcast Licenses - Schedule of Changes in Broadcasting Licenses (Detail) - USD ($)
$ in Thousands
 9 Months Ended 12 Months Ended
Sep. 30, 2018
Dec. 31, 2017
Indefinite-lived Intangible Assets [Line Items]    
Balance, beginning of period before cumulative loss on impairment $ 486,455 $ 494,058
Accumulated loss on impairment, Beginning Balance (105,541) (105,541)
Balance, beginning of period after cumulative loss on impairment 380,914 388,517
Capital projects to improve broadcast signal and strength   5
Balance, end of period before cumulative loss on impairment 484,723 486,455
Accumulated loss on impairment, Ending Balance (105,541) (105,541)
Balance, end of period after cumulative loss on impairment 379,182 380,914
Radio Stations [Member]    
Indefinite-lived Intangible Assets [Line Items]    
Acquisitions of FM translators and construction permits 6,270 191
Dispositions of radio stations (8,013) (7,997)
FM Translators [Member]    
Indefinite-lived Intangible Assets [Line Items]    
Acquisitions of FM translators and construction permits $ 11 $ 198