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Summary of Significant Accounting Policies (Narrative) (Details) $ / shares in Units, $ in Thousands |  |  |  | 1 Months Ended | 3 Months Ended | 9 Months Ended |
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Mar. 04, 2020 $ / shares | Dec. 11, 2019 $ / shares | Sep. 12, 2019 $ / shares | May 30, 2019 $ / shares | Feb. 26, 2019 $ / shares | Sep. 30, 2020 USD ($) item $ / shares shares | Sep. 30, 2019 $ / shares shares | Sep. 30, 2020 USD ($) segment item $ / shares shares | Sep. 30, 2019 $ / shares shares | Dec. 31, 2019 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 |  |  |  |  |  |  |  | 78 |  |
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount | shares |  |  |  |  |  | 0 | 0 | 0 | 0 |
Number of Reportable Segments | item |  |  |  |  |  |  |  | 27 |  |
Special cash dividend declared on Classes A and B Common Stock | $ / shares |  |  |  |  |  | $ 0 | $ 0.30 | $ 0.32 | $ 0.90 |
Number Of Market Serving | item |  |  |  |  |  | 27 |  | 27 |  |
Stock Repurchase Program, Remaining Authorized Repurchase Amount |  |  |  |  |  | $ 19,200 |  | $ 19,200 |  |
Stock Repurchase Program, Authorized Amount |  |  |  |  |  | 75,800 |  | 75,800 |  |
Operating Lease, Right-of-Use Asset |  |  |  |  |  | 6,300 |  | 6,300 |  | $ 6,900
Operating Lease, Liability |  |  |  |  |  | $ 6,595 |  | $ 6,595 |  | $ 7,000
Number of operating segments | segment |  |  |  |  |  |  |  | 1 |  |
Customer relationships [Member] |  |  |  |  |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  |  |  | 3 years |  |
Class A Common Stock |  |  |  |  |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Special cash dividend declared on Classes A and B Common Stock | $ / shares | $ 0.32 | $ 0.30 | $ 0.30 | $ 0.30 | $ 0.30 |  |  |  |  |

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- Definition Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 + Details
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