Short-Term Investments (Tables)

12 Months Ended

Jan. 31, 2019

Investments Debt And Equity Securities [Abstract]

Schedule of Short-Term Investments

At January 31, 2019, short-term investments consisted of the following (in thousands):

			Gross		Gross			Estimated
	Amortized		unrealized		unrealized			fair
	cost		gains		losses			value
Available-for-sale securities:
Certificates of deposits	$	6,001	$	10	$	(1	)	$	6,010
Asset-backed securities		78,682		13		(300	)		78,395
Commercial paper		9,118		1		(2	)		9,117
Corporate notes and bonds		185,409		178		(457	)		185,130
Foreign government bonds		1,502		—		(11	)		1,491
U.S. agency obligations		15,912		2		(2	)		15,912
U.S. treasury securities		243,119		78		(62	)		243,135
Total available-for-sale securities	$	539,743	$	282	$	(835	)	$	539,190

At January 31, 2018, 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	$	67,875	$	—	$	(424	)	$	67,451
Commercial paper		19,926		—		(12	)		19,914
Corporate notes and bonds		160,499		1		(759	)		159,741
Foreign government bonds		1,504		—		(18	)		1,486
Mortgage backed securities		11,555		—		(75	)		11,480
U.S. agency obligations		71,206		1		(76	)		71,131
U.S. treasury securities		110,707		5		(136	)		110,576
Total available-for-sale securities	$	443,272	$	7	$	(1,500	)	$	441,779

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,
	2019		2018
Due in one year or less	$	377,858	$	308,172
Due in greater than one year		161,332		133,607
Total	$	539,190	$	441,779

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

The following table shows the fair values of these available-for-sale securities that have been in a gross unrealized loss position for more than 12 months, aggregated by investment category as of January 31, 2019 (in thousands):   

			Gross
	Fair		unrealized
	value		losses
Certificates of deposits	$	999	$	(1	)
Asset-backed securities		69,131		(300	)
Commercial paper		7,155		(2	)
Corporate notes and bonds		121,006		(457	)
Foreign government bonds		1,490		(11	)
U.S. agency obligations		14,928		(2	)
U.S. treasury securities		130,785		(62	)

The following table shows the fair values of these available-for-sale securities that have been in a gross unrealized loss position for more than 12 months, aggregated by investment category as of January 31, 2018 (in thousands):   

			Gross
	Fair		unrealized
	value		losses
Asset-backed securities	$	65,690	$	(424	)
Commercial paper		19,914		(12	)
Corporate notes and bonds		155,419		(759	)
Foreign government bonds		1,485		(18	)
Mortgage backed securities		11,481		(75	)
U.S. agency obligations		66,655		(76	)
U.S. treasury securities		82,147		(136	)