CONCENTRATION OF CREDIT RISK (Details) $ in Thousands	1 Months Ended	9 Months Ended
	Jun. 30, 2018 USD ($) option	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net, noncurrent		$ 59,117	$ 78,102
Tax credits assigned as collateral for accounts estimated to receive amount of monetization		56,400
ALASKA
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bonds issued to pay estimated liability for Tax Credit certificates	$ 1,000,000
Number of option | option	2
ALASKA | State and Local Jurisdiction | Oil and Gas Purchased Monetized Later Date
Accounts, Notes, Loans and Financing Receivable [Line Items]
Tax credit certificates sold to third party		2,700
Customer A
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for doubtful accounts		19,000
First Option | ALASKA
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchase of the tax credit certificates at a discount rate	10.00%
Second Option | ALASKA
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchase of the tax credit certificates at a cost of capital	5.10%
Customer Concentration Risk | Customer A
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net, noncurrent		$ 59,100
Customer Concentration Risk | Accounts Receivable | Customer A
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percentage		75.50%