Revenue Recognition - Comparison to Amounts if ASC 605 Had Been in Effect (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Comparison to Amounts if ASC 605 Had Been in Effect
Net revenues	$ 147,079	$ 124,464
Operating expenses	102,347	99,108
Operating income	44,732	$ 25,356
ASU 2014-09 | Reclassification
Comparison to Amounts if ASC 605 Had Been in Effect
Net revenues	(3,759)
Operating expenses	(3,759)
ASU 2014-09 | ASC 605 Presentation
Comparison to Amounts if ASC 605 Had Been in Effect
Net revenues	143,320
Operating expenses	98,588
Operating income	$ 44,732