Revenue - Summary of Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation Of Revenue [Line Items]
Gross Revenue	$ 38,451	$ 35,363
Less: Agency commissions and other	4,545	4,013
Net revenue	33,906	31,350
Local, National and Digital
Disaggregation Of Revenue [Line Items]
Gross Revenue	28,628	27,897
Network
Disaggregation Of Revenue [Line Items]
Gross Revenue	2,130	1,480
Special Events
Disaggregation Of Revenue [Line Items]
Gross Revenue	5,120	3,080
Barter
Disaggregation Of Revenue [Line Items]
Gross Revenue	912	1,496
Other
Disaggregation Of Revenue [Line Items]
Gross Revenue	$ 1,661	$ 1,410