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
		Mar. 31, 2019	Mar. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income (Loss)		$ 279	$ (421)
Net Investment Hedge
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income (Loss)		279	(421)
Gain (Loss) Reclassified from Other Comprehensive Income (Loss) to Earnings		0	0
Convertible debt embedded derivative
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	[1]	$ 0	$ 4,547

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