Short-Term Investments (Tables)

9 Months Ended

Oct. 31, 2016

Investments Debt And Equity Securities [Abstract]

Schedule of Short-Term Investments

At October 31, 2016, 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	$	22,839	$	15	$	(6	)	$	22,848
Commercial paper		22,888		7		(10	)		22,885
Corporate notes and bonds		87,348		32		(73	)		87,307
U.S. agency obligations		88,906		40		(15	)		88,931
U.S. treasury securities		82,794		10		(44	)		82,760
Total available-for-sale securities	$	304,775	$	104	$	(148	)	$	304,731

At January 31, 2016, 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	$	5,456	$	—	$	(2	)	$	5,454
Commercial paper		5,970		—		—			5,970
Corporate notes and bonds		38,341		26		(40	)		38,327
U.S. agency obligations		124,626		14		(54	)		124,586
U.S. treasury securities		39,720		4		(37	)		39,687
Total available-for-sale securities	$	214,113	$	44	$	(133	)	$	214,024

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):

	October 31,		January 31,
	2016		2016
Due in one year or less	$	198,245	$	151,214
Due in greater than one year		106,486		62,810
Total	$	304,731	$	214,024

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 October 31, 2016 (in thousands):  

			Gross
	Fair		Unrealized
	Value		Losses
Asset-backed securities	$	12,108	$	(6	)
Commercial paper		10,517		(10	)
Corporate notes and bonds		60,122		(73	)
U.S. agency obligations		20,493		(15	)
U.S. treasury securities		61,156		(44	)

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, 2016 (in thousands):

			Gross
	Fair		Unrealized
	Value		Losses
Asset-backed securities	$	2,249	$	(2	)
Corporate notes and bonds		14,296		(40	)
U.S. agency obligations		82,806		(54	)
U.S. treasury securities		33,486		(37	)