CASH, CASH EQUIVALENTS, RESTRICTED CASH AND MARKETABLE SECURITIES - Summary of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Mar. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Cash and cash equivalents	$ 251,505	$ 304,880	$ 195,423	$ 210,711
Restricted cash	909	846	846	186
Total cash, cash equivalents and restricted cash	$ 252,414	$ 305,726	$ 196,269	$ 210,897