Debt - Long-Term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Less – unamortized original issue discount	$ (12,327)	$ (14,549)
Total debt, net of unamortized discounts	358,298	359,826
Current portion of long-term debt, net of unamortized discounts	(8,438)	(7,500)
Long-term debt, net of unamortized discounts	349,860	352,326
2018 Credit Agreement | 2018 Term Loan
Debt Instrument [Line Items]
Total long-term debt, gross	140,625	144,375
Less – deferred financing costs	(1,997)	(2,281)
Total debt, net of unamortized discounts	138,628	142,094
Senior Convertible Notes 2016
Debt Instrument [Line Items]
Total long-term debt, gross	230,000	230,000
Less – unamortized original issue discount	(7,434)	(8,823)
Less – deferred financing costs	(2,896)	(3,445)
Total debt, net of unamortized discounts	$ 219,670	$ 217,732