Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash paid during the period for:
Interest	$ 635	$ 884	$ 850
Income taxes	3,893	2,864	2,420
Non-cash transactions:
Barter revenue	3,560	3,570	3,618
Barter expense	3,370	3,677	3,367
Purchase of treasury shares in connection with exercise of stock options	0	0	826
Acquisition of property and equipment	28	11	8
Use of treasury shares for 401(k) match	$ 262	$ 252	$ 274