Financial Instruments (Tables)

3 Months Ended

Apr. 30, 2018

Investments, Debt and Equity Securities [Abstract]

Summary of Cash Equivalents, Marketable Securities and Restricted Cash by Significant Investment Categories

The following tables summarize our cash equivalents, marketable securities and restricted cash by significant investment categories as of January 31, 2018 and April 30, 2018 (in thousands):

	As of January 31, 2018
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Cash Equivalents		Marketable Securities		Restricted Cash
Level 1
Money market accounts	$	—	$	—	$	—		$	32,057	$	17,294	$	—	$	14,763
Level 2
U.S. government treasury notes	131,643		—		(651		)	130,992		10,172		120,820		—
U.S. government agencies	47,229		—		(333		)	46,896		—		46,896		—
Corporate debt securities	186,506		116		(1,049		)	185,573		—		185,573		—
Total	$	365,378	$	116	$	(2,033	)	$	395,518	$	27,466	$	353,289	$	14,763

	As of April 30, 2018
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Cash Equivalents		Marketable Securities		Restricted Cash
Level 1
Money market accounts	$	—	$	—	$	—		$	24,747	$	8,248	$	—	$	16,499
Level 2
U.S. government treasury notes	146,112		1		(774		)	145,339		10,419		134,920		—
U.S. government agencies	40,674		—		(390		)	40,284		—		40,284		—
Corporate debt securities	189,083		76		(1,546		)	187,613		—		187,613		—
Total	$	375,869	$	77	$	(2,710	)	$	397,983	$	18,667	$	362,817	$	16,499

Schedule of Amortized Cost and Estimated Fair Value of Marketable Securities by Contractual Maturity

The amortized cost and estimated fair value of our marketable securities are shown below by contractual maturity (in thousands):

	As of April 30, 2018
	Amortized Cost		Fair Value
Due within one year	$	208,672	$	207,951
Due in one to five years	156,778		154,866
Total	$	365,450	$	362,817

Schedule of Gross Unrealized Losses and Fair Values for Investments that were in Continuous Unrealized Loss Position for Less Than 12 Months, Aggregated by Investments Category

The following table presents gross unrealized losses and fair values for those investments that were in a continuous unrealized loss as of April 30, 2018, aggregated by investment category (in thousands):

	Less than 12 months					Greater than 12 months					Total
	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss			Fair Value		Unrealized Loss
U.S. government treasury notes	$	93,195	$	(323	)	$	40,159	$	(451	)	$	133,354	$	(774	)
U.S. government agencies	16,216		(190		)	24,069		(200		)	40,285		(390		)
Corporate debt securities	119,622		(1,188		)	33,349		(358		)	152,971		(1,546		)
Total	$	229,033	$	(1,701	)	$	97,577	$	(1,009	)	$	326,610	$	(2,710	)