FINANCIAL INSTRUMENTS - Offsetting Derivative Assets and Liabilities (Details) - Interest rate swap - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Offsetting of Derivative Assets
Gross Amounts of Recognized Assets	$ 5,238	$ 18,033
Gross Amounts Offset in the Balance Sheet		1,552
Net Amounts of Assets presented in the Balance Sheet	5,238	19,585
Financial Instruments		(1,552)
Net Amount	5,238	18,033
Offsetting of Derivative Liabilities
Gross Amounts Offset in the Balance Sheet		(1,552)
Net Amounts of Liabilities presented in the Balance Sheet		(1,552)
Financial Instruments		1,552
Net Amount		0
Counterparty 1
Offsetting of Derivative Assets
Gross Amounts of Recognized Assets	4,470	15,577
Gross Amounts Offset in the Balance Sheet		1,314
Net Amounts of Assets presented in the Balance Sheet	4,470	16,891
Financial Instruments		(1,314)
Net Amount	4,470	15,577
Offsetting of Derivative Liabilities
Gross Amounts Offset in the Balance Sheet		(1,314)
Net Amounts of Liabilities presented in the Balance Sheet		(1,314)
Financial Instruments		1,314
Net Amount		0
Counterparty 2
Offsetting of Derivative Assets
Gross Amounts of Recognized Assets	304	975
Gross Amounts Offset in the Balance Sheet		80
Net Amounts of Assets presented in the Balance Sheet	304	1,055
Financial Instruments		(80)
Net Amount	304	975
Offsetting of Derivative Liabilities
Gross Amounts Offset in the Balance Sheet		(80)
Net Amounts of Liabilities presented in the Balance Sheet		(80)
Financial Instruments		80
Net Amount		0
Counterparty 3
Offsetting of Derivative Assets
Gross Amounts of Recognized Assets	464	1,481
Gross Amounts Offset in the Balance Sheet		158
Net Amounts of Assets presented in the Balance Sheet	464	1,639
Financial Instruments		(158)
Net Amount	$ 464	1,481
Offsetting of Derivative Liabilities
Gross Amounts Offset in the Balance Sheet		(158)
Net Amounts of Liabilities presented in the Balance Sheet		(158)
Financial Instruments		158
Net Amount		$ 0