Revolving Credit Facility and Long-Term Debt - Principal Balances under Long-term Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 11, 2019	Dec. 31, 2018
Line of Credit Facility [Line Items]
Total long-term debt	$ 384,187		$ 395,152
Collateralized debt facility	7,000	$ 7,000	7,000
Less unamortized debt issuance costs	(313)		(348)
Less current portion	22,000		22,000
Long-term portion	362,187		373,152
Term Loan
Line of Credit Facility [Line Items]
Total long-term debt	68,750		72,500
Revolving Credit Facility
Line of Credit Facility [Line Items]
Total long-term debt	$ 308,750		$ 316,000