Long-Term Debt and Credit Facility - Schedule of Long-term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Subtotal	$ 308,530	$ 347,312
Less – Current maturities of long-term debt	26,548	26,555
Less – Unamortized loan costs	2,713	2,517
Total	279,269	318,240
Term Note
Debt Instrument [Line Items]
Term note, due February 27, 2023, annualized rates of 4.53% and 3.60%, respectively	$ 288,750	$ 308,437
Current effective interest rate	4.53%	3.60%
Line of Credit
Debt Instrument [Line Items]
Line of credit, 4.39% and 3.50%, respectively	$ 19,000	$ 38,000
Current effective interest rate	4.39%	3.50%
Other notes
Debt Instrument [Line Items]
Other notes with interest rates from 3.3% to 7.8%	$ 780	$ 875
Other notes | Minimum
Debt Instrument [Line Items]
Current annualized interest rate	3.30%	3.30%
Other notes | Maximum
Debt Instrument [Line Items]
Current annualized interest rate	7.80%	7.80%