Marketable Securities

9 Months Ended

Oct. 31, 2020

Investments, Debt and Equity Securities [Abstract]

As of October 31, 2020 and January 31, 2020, our marketable securities consisted of the following:


	As of October 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value

	(in thousands)





Commercial paper	$	6,244	$	—	$	—	$	6,244
Agency bonds	409,695		75		(297)		409,473
Corporate and other debt securities	465,399		1,727		(180)		466,946
U.S. government agency securities	144,361		19		(26)		144,354
Treasury bills	114,409		3		(4)		114,408
Marketable securities	$	1,140,108	$	1,824	$	(507)	$	1,141,425


	As of January 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value

	(in thousands)


Commercial paper	$	37,894	$	—	$	—	$	37,894
Agency bonds	141,157		49		(43)		141,163
Corporate and other debt securities	320,407		775		(16)		321,166
U.S. government agency securities	71,794		45		(2)		71,837

Marketable securities	$	571,252	$	869	$	(61)	$	572,060

We review the individual securities that have unrealized losses on a regular basis to evaluate whether or not any security has experienced, or is expected to experience, credit losses resulting in the decline in fair value. We evaluate, among other factors, whether we have the intention to sell any of these marketable securities and whether it is more likely than not that we will be required to sell any of them before recovery of the amortized cost basis. We have not recorded an allowance for credit losses, as we believe any such losses would be immaterial based on the high-grade credit rating for each of our marketable securities as of the end of each period. There were no material realized gains or losses from available-for-sale securities that were reclassified out of accumulated other comprehensive income for the three and nine months ended October 31, 2020 and 2019.

The following table presents the contractual maturities of our marketable securities as of October 31, 2020 and January 31, 2020:


	As of
	October 31, 2020		January 31, 2020

	(in thousands)
Less than one year	$	602,222	$	315,900
Due in one to five years	539,203		256,160
Total	$	1,141,425	$	572,060