CASH, CASH EQUIVALENTS, RESTRICTED CASH AND MARKETABLE SECURITIES - Summary of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Mar. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Cash and cash equivalents	$ 261,736	$ 304,880	$ 210,870	$ 210,711
Restricted cash	846	846	186	186
Total cash, cash equivalents and restricted cash	$ 262,582	$ 305,726	$ 211,056	$ 210,897