DEFERRED COMPENSATION (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Bank deposits held	$ 291,086	$ 390,661	$ 303,116	$ 301,970
Short-term investments [Member] | Mutual funds [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Investments	14,700
Other long-term liabilities [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Deferred compensation liability, noncurrent	$ 15,800	$ 14,100