CASH, CASH EQUIVALENTS, RESTRICTED CASH AND MARKETABLE SECURITIES - Summary of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Cash and cash equivalents	$ 331,912	$ 304,880	$ 244,833	$ 210,711
Restricted cash	910	846	846	186
Total cash, cash equivalents and restricted cash	$ 332,822	$ 305,726	$ 245,679	$ 210,897