CONCENTRATION OF CREDIT RISK (Details) $ in Thousands	1 Months Ended	3 Months Ended	6 Months Ended
	Jun. 30, 2018 USD ($) option	Jun. 30, 2018 USD ($) option	Jun. 30, 2018 USD ($) option	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net, noncurrent	$ 59,117	$ 59,117	$ 59,117		$ 78,102
Purchase of oil and natural gas		19,710	45,715
Tax credits assigned as collateral for accounts estimated to receive amount of monetization	56,500	56,500	56,500
Provision for doubtful accounts		$ 19,000	$ 19,120	$ 0
State of 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	2	2
State of ALASKA | State and Local Jurisdiction | Oil and Gas Purchased Include Slight Discount
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchase of oil and natural gas			$ 14,900
State of 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	2,700
First Option | State of ALASKA
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchase of the tax credit certificates at a discount rate	10.00%
Second Option | State of 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	$ 78,100	$ 78,100	$ 78,100
Customer Concentration Risk | Accounts Receivable | Customer A
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percentage			86.10%