LONG-TERM DEBT, DERIVATIVES AND LETTERS OF CREDIT - Amounts Recognized in Other Comprehensive Income (Loss), and Reclassified Into Income (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income (Loss)		$ (184)	$ 788	$ 95	$ 367
Net Investment Hedge
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income (Loss)		(184)	788	95	367
Gain (Loss) Reclassified from Other Comprehensive Income (Loss) to Earnings		0	0	0	0
Convertible debt embedded derivative
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	[1]	$ 0	$ (29,330)	$ 0	$ (24,783)

[1] Reflected as “Loss on convertible debt embedded derivative” in the condensed consolidated statements of operations.