Debt - Long-Term Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Less – unamortized original issue discount	$ (13,444)	$ (14,549)
Total debt, net of unamortized discounts	359,056	359,826
Current portion of long-term debt, net of unamortized discounts	(7,500)	(7,500)
Long-term debt, net of unamortized discounts	351,556	352,326
2018 Credit Agreement | 2018 Term Loan
Debt Instrument [Line Items]
Total long-term debt, gross	142,500	144,375
Less - deferred financing costs	(2,139)	(2,281)
Total debt, net of unamortized discounts	140,361	142,094
Senior Convertible Notes 2016
Debt Instrument [Line Items]
Total long-term debt, gross	230,000	230,000
Less – unamortized original issue discount	(8,133)	(8,823)
Less - deferred financing costs	(3,172)	(3,445)
Total debt, net of unamortized discounts	$ 218,695	$ 217,732