ACCOUNTS RECEIVABLE SECURITIZATION (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Short-term Debt [Line Items]
Costs associated with receivables facility			$ 20,169,000	$ 1,767,000
Line of Credit | Accounts Receivable Securitization Facility
Short-term Debt [Line Items]
Maximum borrowing capacity	$ 100,000,000		$ 100,000,000
Unused commitment fee (as a percent)			0.60%
Accounts receivable eligible for securitization	33,780,000		$ 33,780,000		$ 37,869,000
Outstanding borrowings	0		0		0
Letters of credit outstanding	37,695,000		37,695,000		52,536,000
Borrowings and issuance of letters of credit remaining capacity	0		0		0
Cash collateral	3,915,000		3,915,000		14,667,000
Costs associated with receivables facility	370,000	$ 751,000	$ 860,000	$ 1,526,000
Minimum | Line of Credit | Accounts Receivable Securitization Facility
Short-term Debt [Line Items]
Security facility program fee (as a percent)			2.00%
Maximum | Line of Credit | Accounts Receivable Securitization Facility
Short-term Debt [Line Items]
Security facility program fee (as a percent)			2.50%
Restricted Cash | Line of Credit | Accounts Receivable Securitization Facility
Short-term Debt [Line Items]
Cash collateral	$ 3,915,000		$ 3,915,000		$ 14,667,000