Nature of Business and Significant Accounting Policies - Concentration Of Risk - (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) item	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Revenue | Customer concentration risk
Concentration risk
Number of distributors who accounted for more than 10% | item	2
Programming rights | Level 3 | Fair Value, Measurements, Nonrecurring
Fair value of financial instruments:
Adjustments to fair value | $	$ 0	$ 0	$ 0