DERIVATIVES AND HEDGING - Summary of Freestanding Derivative Instruments on Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Gains and losses from freestanding derivative instruments	$ (14,723)	$ (1,691)	$ (18,279)	$ (20,483)
Investment income | Not Designated as Hedging Instrument | Foreign-currency forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains and losses from freestanding derivative instruments	(8,455)	6,530	(9,328)	(2,371)
General and administrative expense | Not Designated as Hedging Instrument | Foreign-currency forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains and losses from freestanding derivative instruments	$ (6,268)	$ (8,221)	$ (8,951)	$ (18,112)