Long-term Debt, Line of Credit and Derivatives - Obligations under Debt Arrangements (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Sep. 30, 2017	Jun. 30, 2018	Dec. 31, 2017	Aug. 05, 2015
Debt Instrument [Line Items]
Debt issuance costs			$ 4,500
Debt issuance expense	$ 200	$ 600	500
Principal, current	31,500		31,500	$ 23,500
Principal	90,000		90,000	88,750
Deferred Issuance Costs, current	(757)		(757)	(744)
Deferred Issuance Costs	(2,163)		(2,163)	(2,809)
Net Value, current	30,743		30,743	22,756
Net Value, long-term	57,094		57,094	63,185
Total debt	$ 87,837		$ 87,837	85,941
Line of Credit
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					4.75%
Revolving line of credit | Line of Credit
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.88%		3.88%
Principal, current	$ 18,000		$ 18,000	10,000
Deferred Issuance Costs, current	(433)		(433)	(317)
Net Value, current	17,567		17,567	9,683
Term loan - current | Loans Payable
Debt Instrument [Line Items]
Principal, current	13,500		13,500	13,500
Deferred Issuance Costs, current	(324)		(324)	(427)
Net Value, current	13,176		13,176	13,073
Term loan - long-term | Loans Payable
Debt Instrument [Line Items]
Principal, long-term	58,500		58,500	65,250
Deferred Issuance Costs, long-term	(1,406)		(1,406)	(2,065)
Net Value, long-term	$ 57,094		$ 57,094	$ 63,185