Nature of Business and Significant Accounting Policies - Barter (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Barter transactions:
Barter revenue	$ 934	$ 811	$ 1,311
Barter expense	(756)	(791)	(1,075)
Barter revenue and expense	178	20	236
Advertising and Marketing costs:
Advertising and marketing costs	$ 3,800	$ 3,500	$ 2,400