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Summary of Significant Accounting Policies (Narrative) (Details) | 3 Months Ended | 9 Months Ended |
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Sep. 30, 2021 USD ($) item shares | Sep. 30, 2020 shares | Sep. 30, 2021 USD ($) item segment shares | Sep. 30, 2020 shares | Dec. 31, 2020 USD ($)
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |
Number Of FM Radio Stations | item |  |  | 79 |  |
Number Of AM Radio Stations |  |  | 34 |  |
Number Of Metro Signals |  |  | 79 |  |
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount | shares | 0 | 0 | 0 | 0 |
Number of reportable segments | segment |  |  | 1 |  |
Number Of Market Serving | item | 27 |  | 27 |  |
Operating Lease, Right-of-Use Asset | $ | $ 5,500,000 |  | $ 5,500,000 |  | $ 6,600,000
Number of operating segments | segment |  |  | 1 |  |
Operating Lease, Liability | $ | 5,841,000 |  | $ 5,841,000 |  | 6,900,000
Allowance for doubtful accounts receivable | $ | $ 385,000 |  | $ 385,000 |  | $ 648,000
Number of Radio Markets | item |  |  | 27 |  |
Customer relationships [Member] |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  |  | 3 years |  |

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- Definition Amount of allowance for credit loss on accounts receivable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5074-111524 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446 + Details
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