Short-Term Investments (Tables)

12 Months Ended

Jan. 31, 2016

Investments Debt And Equity Securities [Abstract]

Schedule of Short-Term Investments

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

At January 31, 2015, 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	$	9,323	$	—	$	(4	)	$	9,319
Commercial paper		3,394		—		—			3,394
Corporate notes and bonds		45,990		18		(19	)		45,989
U.S. agency obligations		199,822		92		(3	)		199,911
U.S. treasury securities		9,999		8		—			10,007
Total available-for-sale securities	$	268,528	$	118	$	(26	)	$	268,620

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):

	January 31,
	2016		2015
Due in one year or less	$	151,214	$	224,263
Due in greater than one year		62,810		44,357
Total	$	214,024	$	268,620

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 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	)

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, 2015 (in thousands):   

			Gross
	Fair		Unrealized
	Value		Losses
Asset-backed securities	$	9,319	$	(4	)
Corporate notes and bonds		23,239		(19	)
U.S. agency obligations		18,398		(3	)