Short-Term Investments (Tables)

6 Months Ended

Jul. 31, 2016

Investments Debt And Equity Securities [Abstract]

Schedule of Short-Term Investments

At July 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	$	16,660	$	35	$	—		$	16,695
Commercial paper		16,062		—		—			16,062
Corporate notes and bonds		74,196		72		(23	)		74,245
U.S. agency obligations		101,803		64		(12	)		101,855
U.S. treasury securities		60,289		45		(1	)		60,333
Total available-for-sale securities	$	269,010	$	216	$	(36	)	$	269,190

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):

	July 31,		January 31,
	2016		2016
Due in one year or less	$	185,713	$	151,214
Due in greater than one year		83,477		62,810
Total	$	269,190	$	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 July 31, 2016 (in thousands):  

			Gross
	Fair		Unrealized
	Value		Losses
Asset-backed securities	$	46	$	—
Corporate notes and bonds		19,792		(23	)
U.S. agency obligations		12,430		(12	)
U.S. treasury securities		5,017		(1	)

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	)