Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash paid during the period for:
Interest	$ 311	$ 635	$ 884
Income taxes	1,099	3,893	2,864
Non-cash transactions:
Barter revenue	2,014	3,560	3,570
Barter expense	1,881	3,370	3,677
Acquisition of property and equipment	6	28	11
Use of treasury shares for 401(k) match	$ 250	$ 262	$ 252