FINANCIAL INSTRUMENTS - Offsetting Derivative Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Offsetting of Derivative Assets
Gross Amounts of Recognized Assets	$ 15,603	$ 5,238
Net Amounts of Assets presented in the Balance Sheet	15,603	5,238
Net Amount	15,603	5,238
Counterparty 1
Offsetting of Derivative Assets
Gross Amounts of Recognized Assets	13,675	4,470
Net Amounts of Assets presented in the Balance Sheet	13,675	4,470
Net Amount	13,675	4,470
Counterparty 2
Offsetting of Derivative Assets
Gross Amounts of Recognized Assets	670	304
Net Amounts of Assets presented in the Balance Sheet	670	304
Net Amount	670	304
Counterparty 3
Offsetting of Derivative Assets
Gross Amounts of Recognized Assets	1,258	464
Net Amounts of Assets presented in the Balance Sheet	1,258	464
Net Amount	$ 1,258	$ 464