Marketable Securities (Tables)

12 Months Ended

Mar. 31, 2018

Investments Debt And Equity Securities [Abstract]

Schedule of Marketable Securities

a. Marketable securities:

	March 31,
	2018		2017
Short-term  marketable securities	$	549,821	$	3,548
Long-term marketable securities		225,639		—
	$	775,460	$	3,548

Summary of Both Short-Term and Long-Term Marketable Securities

a. The following is a summary of both short-term and long-term marketable securities by type:

	March 31,
	2018							2017
	Amortized		Gross unrealized			Market		Amortized		Gross unrealized			Market
	cost		loss			value		cost		loss			value
Marketable securities:
Bonds	$	386,332	$	(2,027	)	$	384,305	$	—	$	—		$	—
Government Securities		177,657		(555	)		177,102		3,617		(69	)		3,548
Commercial Paper		51,432		(1	)		51,431		—		—			—
Other Securities		162,672		(50	)		162,622		—		—			—
Total marketable securities	$	778,093	$	(2,633	)	$	775,460	$	3,617	$	(69	)	$	3,548

Estimated Fair Value of Marketable Securities by Contractual Maturity

The estimated fair value of marketable securities as of March 31, 2018 and 2017, by contractual maturity, are as follows:

	March 31,
	2018				2017
	Amortized		Market		Amortized		Market
	cost		Value		cost		Value
Available-for-sale marketable securities:
Matures in less than five years	$	776,932	$	774,300	$	1,181	$	1,001
Matures in more than five years		1,161		1,160		2,436		2,547
	$	778,093	$	775,460	$	3,617	$	3,548