FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Debt) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Carrying Value
Fair value disclosure
Debt obligations	$ 290,206	$ 268,441
Fair Value
Fair value disclosure
Debt obligations	288,309	267,131
Level 2 | Credit Facility | Carrying Value
Fair value disclosure
Debt obligations	70,000	70,000
Level 2 | Credit Facility | Fair Value
Fair value disclosure
Debt obligations	70,000	70,000
Level 2 | Accounts receivable securitization borrowings | Carrying Value
Fair value disclosure
Debt obligations	45,000	45,000
Level 2 | Accounts receivable securitization borrowings | Fair Value
Fair value disclosure
Debt obligations	45,000	45,000
Level 2 | Notes payable | Carrying Value
Fair value disclosure
Debt obligations	175,206	153,441
Level 2 | Notes payable | Fair Value
Fair value disclosure
Debt obligations	$ 173,309	$ 152,131