Nature of Business and Significant Accounting Policies - Barter, Advertising and Marketing Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Barter transactions:
Barter revenue	$ 434	$ 872
Barter expense	(419)	(557)
Barter revenue and expense	15	315
Advertising and Marketing costs:
Advertising and marketing costs	$ 3,100	$ 3,700