DERIVATIVE CONTRACTS AND COLLATERALIZED INDEBTEDNESS - Location of Assets and Liabilities Within the Consolidated Balance Sheets (Details) - Not Designated as Hedging Instruments - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Asset Derivatives	$ 0	$ 111,319
Liability Derivatives	289,634	132,978
Interest Rate Swap | Current derivative contracts
Derivatives, Fair Value [Line Items]
Asset Derivatives	0	1,975
Interest Rate Swap | Short-term liabilities under derivative contracts
Derivatives, Fair Value [Line Items]
Liability Derivatives	478	70
Interest Rate Swap | Long-term liabilities under derivative contracts
Derivatives, Fair Value [Line Items]
Liability Derivatives	(171,847)	(132,908)
Prepaid forward contracts | Long-term derivative contracts
Derivatives, Fair Value [Line Items]
Asset Derivatives	0	109,344
Prepaid forward contracts | Long-term liabilities under derivative contracts
Derivatives, Fair Value [Line Items]
Liability Derivatives	$ (117,309)	$ 0