Long-term Debt, Line of Credit and Derivatives - Obligations under Debt Arrangements (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2017	Aug. 05, 2015
Debt Instrument [Line Items]
Debt issuance costs	$ 4,500
Debt issuance expense	500	$ 600	$ 200
Principal, current	18,500			$ 23,500
Principal	80,375			88,750
Deferred Issuance Costs, current	(569)			(744)
Deferred Issuance Costs	(2,472)			(2,809)
Net Value, current	17,931			22,756
Net Value, long-term	59,972			63,185
Total debt	$ 77,903			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	3.81%
Principal, current	$ 5,000			10,000
Deferred Issuance Costs, current	(154)			(317)
Net Value, current	4,846			9,683
Term loan - current | Loans Payable
Debt Instrument [Line Items]
Principal, current	13,500			13,500
Deferred Issuance Costs, current	(415)			(427)
Net Value, current	13,085			13,073
Term loan - long-term | Loans Payable
Debt Instrument [Line Items]
Principal, long-term	61,875			65,250
Deferred Issuance Costs, long-term	(1,903)			(2,065)
Net Value, long-term	$ 59,972			$ 63,185