Long-Term Debt (Schedule of Long Term Debt) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Jul. 01, 2016
Unamortized deferred financing costs	$ (22,738)	$ (24,063)
Total long-term debt, net of unamortized deferred financing costs	605,037	610,787
Less: current portion of long-term debt	28,300	28,300
Long term debt, noncurrent	576,737	582,487
BoA Credit Agreement [Member]
Total long-term debt, net of unamortized deferred financing costs			$ 258,000
BoA Term Loans [Member]
Secured Term Loans	512,775	519,850
Revolving Loans [Member]
Revolving Credit Facility	$ 115,000	$ 115,000
Total long-term debt, net of unamortized deferred financing costs			$ 115,000