Short-Term Investments (Tables)

3 Months Ended

Apr. 30, 2017

Investments Debt And Equity Securities [Abstract]

Schedule of Short-Term Investments

At April 30, 2017, short-term investments consisted of the following (in thousands):

			Gross		Gross			Estimated
	Amortized		unrealized		unrealized			fair
	cost		gains		losses			value
Available-for-sale securities:
Asset-backed securities	$	18,873	$	3	$	(15	)	$	18,861
Commercial paper		13,460		—		(1	)		13,459
Corporate notes and bonds		98,735		22		(64	)		98,693
U.S. agency obligations		86,316		—		(104	)		86,212
U.S. treasury securities		81,219		5		(192	)		81,032
Total available-for-sale securities	$	298,603	$	30	$	(376	)	$	298,257

At January 31, 2017, short-term investments consisted of the following (in thousands):  

			Gross		Gross			Estimated
	Amortized		unrealized		unrealized			fair
	cost		gains		losses			value
Available-for-sale securities:
Asset-backed securities	$	20,729	$	5	$	(16	)	$	20,718
Commercial paper		20,567		4		(1	)		20,570
Corporate notes and bonds		92,843		14		(101	)		92,756
U.S. agency obligations		87,091		12		(51	)		87,052
U.S. treasury securities		80,277		4		(111	)		80,170
Total available-for-sale securities	$	301,507	$	39	$	(280	)	$	301,266

Summary of Estimated Fair Value of Short-Term Investments, Designated as Available-for-Sale and Classified by Contractual Maturity

The following table summarizes the estimated fair value of our short-term investments, designated as available-for-sale and classified by the contractual maturity date of the securities as of the dates shown (in thousands):

	April 30,		January 31,
	2017		2017
Due in one year or less	$	256,380	$	225,183
Due in greater than one year		41,877		76,083
Total	$	298,257	$	301,266

Schedule of Fair Values and Gross Unrealized Losses of Available-for-Sale Securities Aggregated by Investment Category

The following table shows the fair values and the gross unrealized losses of these available-for-sale securities aggregated by investment category as of April 30, 2017 (in thousands):  

			Gross
	Fair		unrealized
	value		losses
Asset-backed securities	$	15,108	$	(15	)
Commercial paper		6,465		(1	)
Corporate notes and bonds		61,584		(64	)
U.S. agency obligations		82,193		(104	)
U.S. treasury securities		78,037		(192	)

The following table shows the fair values and the gross unrealized losses of these available-for-sale securities aggregated by investment category as of January 31, 2017 (in thousands):

			Gross
	Fair		unrealized
	value		losses
Asset-backed securities	$	14,027	$	(16	)
Commercial paper		5,694		(1	)
Corporate notes and bonds		67,220		(101	)
U.S. agency obligations		40,549		(51	)
U.S. treasury securities		68,704		(111	)