Long-term Debt, Line of Credit and Derivatives - Obligations under Debt Arrangements (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Debt issuance costs	$ 900
Debt issuance expense	2,200
Principal, current	41,000	$ 23,500
Principal	97,250	88,750
Deferred Issuance Costs, current	(350)	(744)
Deferred Issuance Costs	(830)	(2,809)
Net Value, current	40,650	22,756
Net Value, long-term	55,770	63,185
Total debt	$ 96,420	85,941
Revolving line of credit | Line of Credit
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.98%
Principal, current	$ 38,000	10,000
Deferred Issuance Costs, current	(324)	(317)
Net Value, current	37,676	9,683
Term loan - current | Loans Payable
Debt Instrument [Line Items]
Principal, current	3,000	13,500
Deferred Issuance Costs, current	(26)	(427)
Net Value, current	2,974	13,073
Term loan - long-term | Loans Payable
Debt Instrument [Line Items]
Principal, long-term	56,250	65,250
Deferred Issuance Costs, long-term	(480)	(2,065)
Net Value, long-term	$ 55,770	$ 63,185