CASH, CASH EQUIVALENTS, AND INVESTMENTS (Tables)

9 Months Ended

Dec. 31, 2017

CASH, CASH EQUIVALENTS AND INVESTMENTS [Abstract]

Cash, Cash Equivalents, and Investments

The following tables summarize the Company’s cash and available-for-sale securities’ amortized cost, gross unrealized gains, gross unrealized losses, and fair value by significant investment category recorded as cash and cash equivalents, short-term, or long-term investments as of December 31, 2017 and March 31, 2017 (in thousands):

December 31, 2017	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Cash & Cash Equivalents		Short-term investments (due in 1 year or less)		Long-term investments (due in 1 to 3 years)
Cash	$	272,063	$	—	$	—		$	272,063	$	272,063	$	—	$	—
Level 1:
Mutual Funds	14,298		399		(70		)	14,627		—		14,627		—
US Treasury Notes	71,684		—		(210		)	71,474		4,998		42,348		24,128
Money Market Funds	239		—		—			239		239		—		—
Subtotal	86,221		399		(280		)	86,340		5,237		56,975		24,128
Level 2:
Government Agency Securities	56,667		—		(276		)	56,391		—		31,300		25,091
Commercial Paper	32,944		—		—			32,944		2,993		29,951		—
Corporate Bonds	142,148		45		(375		)	141,818		—		77,175		64,643
Certificates of Deposits ("CDs")	28,383		—		(3		)	28,380		—		23,372		5,008
Subtotal	260,142		45		(654		)	259,533		2,993		161,798		94,742
Total cash, cash equivalents and investments measured at fair value	$	618,426	$	444	$	(934	)	$	617,936	$	280,293	$	218,773	$	118,870

March 31, 2017	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Cash & Cash Equivalents		Short-term investments (due in 1 year or less)		Long-term investments (due in 1 to 3 years)
Cash	$	295,877	$	—	$	—		$	295,877	$	295,877	$	—	$	—
Level 1:
Mutual Funds	12,079		352		(32		)	12,399		—		12,399		—
US Treasury Notes	35,960		—		(68		)	35,892		—		17,560		18,332
Money Market Funds	—		—		—			—		—		—		—
Subtotal	48,039		352		(100		)	48,291		—		29,959		18,332
Level 2:
Government Agency Securities	54,415		20		(164		)	54,271		—		15,309		38,962
Commercial Paper	47,152		—		—			47,152		6,093		41,059		—
Corporate Bonds	141,508		64		(224		)	141,348		—		73,676		67,672
Certificates of Deposits ("CDs")	20,383		3		—			20,386		—		18,176		2,210
Subtotal	263,458		87		(388		)	263,157		6,093		148,220		108,844
Total cash, cash equivalents and investments measured at fair value	$	607,374	$	439	$	(488	)	$	607,325	$	301,970	$	178,179	$	127,176