LONG‑TERM DEBT - Schedule of Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total debt	$ 72,942	$ 179,443
Less deferred loan costs, net of amortization	0	3,116
Subtotal	72,942	176,327
Less current portion of long-term debt	15,764	16,920
Total long-term debt, net of deferred loan costs	57,178	159,407
Line of Credit
Debt Instrument [Line Items]
Total debt	0	13,500
Line of Credit | ABL Credit Facility
Debt Instrument [Line Items]
Total debt	55,000	0
6.25% Term loan | 6.25% Term loan
Debt Instrument [Line Items]
Total debt	$ 0	146,750
Debt instrument, interest rate, stated percentage	6.25%
Equipment financing | Equipment financing
Debt Instrument [Line Items]
Total debt	$ 17,942	$ 19,193
Subtotal	$ 4,700