LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Securitization program (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financing Arrangements
Long-term debt	$ 266,837	$ 284,224
Outstanding letters of credit	12,300
Accounts receivable securitization borrowings
Financing Arrangements
Maximum borrowing capacity	125,000
Additional borrowing capacity that may be requested	25,000
Outstanding letters of credit	11,700
Remaining borrowing capacity	$ 113,300