Summary of Significant Accounting Policies (Details Textual)									1 Months Ended				12 Months Ended
	Dec. 07, 2017 USD ($) $ / shares	Sep. 13, 2017 USD ($) $ / shares	May 03, 2017 USD ($) $ / shares	Mar. 03, 2017 USD ($) $ / shares	Jun. 01, 2016 USD ($) $ / shares	Mar. 02, 2016 USD ($) $ / shares	Sep. 02, 2015 USD ($) $ / shares	Jun. 10, 2015 USD ($) $ / shares	Nov. 21, 2016 USD ($) $ / shares	Aug. 30, 2016 USD ($) $ / shares	Nov. 17, 2015 USD ($) $ / shares	Mar. 25, 2015 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares
Summary Of Significant Accounting Policies [Line Items]
Number of stock options outstanding having antidilutive effect | shares													0	0	0
Concentration Risk, Market Risk													46.00%	48.00%	46.00%
Interest expense related to the amortization of debt issuance costs													$ 53,000	$ 53,000	$ 131,000
Write-off of debt issuance costs													0	0	$ 557,000
Net book value of deferred costs													$ 138,000	$ 191,000
Treasury Stock, Shares, Acquired | shares													37,141	18,612	129,384
Treasury Stock Acquired, Average Cost Per Share | $ / shares													$ 47.72	$ 40.06	$ 36.53
Special cash dividend declared on Classes A and B Common Stock | $ / shares	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.25	$ 0.25	$ 0.20	$ 0.20	$ 0.30	$ 0.30	$ 0.25	$ 0.20	$ 2	$ 1.3	$ 1.1
Dividend paid	$ 6,500,000	$ 1,800,000	$ 1,800,000	$ 1,800,000	$ 1,500,000	$ 1,500,000	$ 1,200,000	$ 1,200,000	$ 2,900,000	$ 1,800,000	$ 2,900,000	$ 1,200,000
Number Of Broadcast Licenses													108
Number Of Market Serving													26
Dividends Payable, Amount Per Share | $ / shares	$ 0.80										$ 0.25
Deferred Tax Assets, Net of Valuation Allowance, Current, Total													$ 300,000	$ 1,022,000
Continuing Operations [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation expense													5,391,000	5,234,000	$ 5,194,000
Advertising and promotion costs													2,441,000	2,633,000	2,475,000
Discontinued Operations [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation expense													445,000	1,387,000	1,399,000
Advertising and promotion costs													240,000	$ 341,000	$ 328,000
Class A Common Stock [Member]
Summary Of Significant Accounting Policies [Line Items]
Stock Repurchase Program, Remaining Authorized Repurchase Amount													22,400,000
Minimum [Member] | Class A Common Stock [Member]
Summary Of Significant Accounting Policies [Line Items]
Stock Repurchase Program, Authorized Amount													60,000,000
Maximum [Member] | Class A Common Stock [Member]
Summary Of Significant Accounting Policies [Line Items]
Stock Repurchase Program, Authorized Amount													$ 75,800,000
Favorable Lease Agreements [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortized over the lives of the leases term range													5 years
Favorable Lease Agreements [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortized over the lives of the leases term range													26 years