Segment Information - Disaggregation of Revenue Generating Activities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 292,163	$ 254,191
Core advertising
Disaggregation of Revenue [Line Items]
Total operating revenues	173,361	166,553
Political
Disaggregation of Revenue [Line Items]
Total operating revenues	880	2,584
Retransmission and carriage
Disaggregation of Revenue [Line Items]
Total operating revenues	87,283	71,060
Other
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 30,639	$ 13,994