FAIR VALUE MEASUREMENTS - Schedule of Reconciliation of Changes in Fair Value of Level 3 Financial Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Payments received	$ 0	$ 12,864	$ 9,306
Payments made	660	0	0
Fair value, measurements, recurring | Contingent Purchase Consideration
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(5,449)	(7,293)
Additions to Level 3	(523)	(660)
Increase in fair value and accretion expense (included within research and development expense)	(152)	(153)
Gross presentation of contingently returnable consideration to contingent purchase consideration		(3,910)
Payments made	660	6,567
Ending balance	(5,464)	(5,449)	(7,293)
Fair value, measurements, recurring | Contingently Returnable Consideration
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 0	(16,131)
Decrease in fair value		(610)
Gross presentation of contingently returnable consideration to contingent purchase consideration		3,910
Payments received		(19,431)
Ending balance		$ 0	$ (16,131)