Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue.
Revenue from Contract with Customer, Including Assessed Tax	$ 28,845	$ 24,143	$ 79,192	$ 67,060
Revenue, Remaining Performance Obligation, Optional Exemption, Performance Obligation [true false]			true
Broadcast Advertising Revenue, Net [Member]
Revenue.
Revenue from Contract with Customer, Including Assessed Tax	24,970	22,124	$ 69,921	61,119
Digital Advertising Revenue [Member]
Revenue.
Revenue from Contract with Customer, Including Assessed Tax	1,984	845	4,620	2,412
Other Revenue [Member]
Revenue.
Revenue from Contract with Customer, Including Assessed Tax	$ 1,891	$ 1,174	$ 4,651	$ 3,529