FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Debt) (Details) $ in Thousands	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Carrying Value
Fair value disclosure
Financial instruments	$ 554,604	$ 345,522
Fair Value
Fair value disclosure
Financial instruments	562,258	350,894
Credit Facility | Carrying Value | Level 2
Fair value disclosure
Financial instruments	250,000	70,000
Credit Facility | Fair Value | Level 2
Fair value disclosure
Financial instruments	250,000	70,000
Accounts receivable securitization borrowings | Carrying Value | Level 2
Fair value disclosure
Financial instruments	85,000	40,000
Accounts receivable securitization borrowings | Fair Value | Level 2
Fair value disclosure
Financial instruments	85,000	40,000
Notes payable | Carrying Value | Level 2
Fair value disclosure
Financial instruments	197,888	213,504
Notes payable | Fair Value | Level 2
Fair value disclosure
Financial instruments	$ 200,581	$ 216,432
New England Pension Fund withdrawal liability | Discount Rate
Fair value disclosure
Measurement input	0.023	0.034
New England Pension Fund withdrawal liability | Carrying Value | Level 2
Fair value disclosure
Financial instruments	$ 21,716	$ 22,018
New England Pension Fund withdrawal liability | Fair Value | Level 2
Fair value disclosure
Financial instruments	$ 26,677	$ 24,462