FINANCIAL INSTRUMENTS - Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation (Details) - Fair Value, Inputs, Level 3 $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Level 3 liability, beginning of period	$ 362,959
Change in fair value	21,658
Level 3 liability, end of period	$ 384,617