Short-Term Investments

12 Months Ended

Jan. 31, 2021

Investments, Debt and Equity Securities [Abstract]

At January 31, 2021, short-term investments consisted of the following (in thousands):


	Amortized cost		Gross unrealized gains		Gross unrealized losses		Estimated fair value
Available-for-sale securities:
Certificates of deposits	$	17,350	$	15	$	(1)	$	17,364
Asset-backed securities	125,833		745		(2)		126,576
Commercial paper	57,390		8		(2)		57,396
Corporate notes and bonds	428,710		2,360		(23)		431,047
Foreign government bonds	31,855		45		(2)		31,898
U.S. agency obligations	52,756		119		—		52,875
U.S. treasury securities	215,379		587		—		215,966
Total available-for-sale securities	$	929,273	$	3,879	$	(30)	$	933,122

At January 31, 2020, short-term investments consisted of the following (in thousands):


	Amortized cost		Gross unrealized gains		Gross unrealized losses		Estimated fair value
Available-for-sale securities:
Certificates of deposits	$	3,500	$	3	$	—	$	3,503
Asset-backed securities	100,419		396		(1)		100,814
Commercial paper	19,965		5		(1)		19,969
Corporate notes and bonds	234,664		1,552		(2)		236,214
Foreign government bonds	3,397		10		—		3,407
U.S. treasury securities	245,509		599		—		246,108
Total available-for-sale securities	$	607,454	$	2,565	$	(4)	$	610,015

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,
	2021		2020
Due in one year or less	$	428,155	$	247,592
Due in greater than one year	504,967		362,423
Total short-term investments	$	933,122	$	610,015

We have not recorded an allowance for credit losses, as we believe any such losses would be immaterial based on the high credit quality of our investments. We intend to hold our securities to maturity and it is more likely than not we will hold these securities until recovery of the cost basis.

The following table shows the fair values of available-for-sale securities which were in an unrealized loss position, aggregated by investment category, as of January 31, 2021 (in thousands):


	Held for less than 12 months
	Fair value		Gross unrealized losses
Certificates of deposits	$	3,749	$	(2)
Asset-backed securities	3,318		(1)
Commercial paper	17,626		(2)
Corporate notes and bonds	29,558		(23)
Foreign government bonds	2,679		(2)

The following table shows the fair values of available-for-sale securities which were in an unrealized loss position, aggregated by investment category, as of January 31, 2020 (in thousands):


	Held for less than 12 months
	Fair value	Gross unrealized losses

Asset-backed securities	999	(1)
Commercial paper	5,589	(1)
Corporate notes and bonds	6,104	(2)

Asset values and gross unrealized losses of available-for-sale securities held for more than 12 months as of January 31, 2021 and 2020 were immaterial. There were no impairments considered other-than-temporary as of January 31, 2021 and 2020 as it is more likely than not we will hold these securities until recovery of the cost basis.