CASH, CASH EQUIVALENTS AND MARKETABLE SECURITIES - Summary of Marketable Securities Classified as Short-term and Long-term (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Cash, Cash Equivalents and Marketable Securities [Line Items]
Amortized Cost	$ 77,339	$ 78,003
Unrealized Gains	17	(62)
Fair Value	77,356	77,941
U.S. government and municipal obligations
Cash, Cash Equivalents and Marketable Securities [Line Items]
Fair Value	27,622	42,186
Commercial paper
Cash, Cash Equivalents and Marketable Securities [Line Items]
Fair Value	48,722	33,003
Corporate bonds
Cash, Cash Equivalents and Marketable Securities [Line Items]
Fair Value	1,012	2,752
Short-term marketable securities
Cash, Cash Equivalents and Marketable Securities [Line Items]
Amortized Cost	76,332	78,003
Unrealized Gains	12	(62)
Fair Value	76,344	77,941
Short-term marketable securities | U.S. government and municipal obligations
Cash, Cash Equivalents and Marketable Securities [Line Items]
Amortized Cost	27,610	42,246
Unrealized Gains	12	(60)
Fair Value	27,622	42,186
Short-term marketable securities | Commercial paper
Cash, Cash Equivalents and Marketable Securities [Line Items]
Amortized Cost	48,722	33,003
Unrealized Gains	0	0
Fair Value	48,722	33,003
Short-term marketable securities | Corporate bonds
Cash, Cash Equivalents and Marketable Securities [Line Items]
Amortized Cost		2,754
Unrealized Gains		(2)
Fair Value		2,752
Long-term marketable securities
Cash, Cash Equivalents and Marketable Securities [Line Items]
Amortized Cost	1,007	0
Unrealized Gains	5	0
Fair Value	1,012	$ 0
Long-term marketable securities | Corporate bonds
Cash, Cash Equivalents and Marketable Securities [Line Items]
Amortized Cost	1,007
Unrealized Gains	5
Fair Value	$ 1,012