Marketable Securities (Tables)

12 Months Ended

Jan. 31, 2021

Investments Debt And Equity Securities [Abstract]

Amortized Cost, Gross Unrealized Gains (Losses) and Fair Value of Available-For-Sale Securities

The amortized cost, gross unrealized gains (losses) and fair values of available-for-sale securities by major security type and class of security as of January 31, 2021 and 2020 are as follows:

	Amortized Cost		Unrealized Gains		Unrealized (Losses)			Fair Value
As of January 31, 2021
Short-term Investments:
Municipal and pre-refunded municipal bonds	$	127,097	$	11	$	(53	)	$	127,055
Corporate bonds		38,695		1		(48	)		38,648
Commercial paper		8,992		—		—			8,992
		174,784		12		(101	)		174,695
Long-term Investments:
Municipal and pre-refunded municipal bonds		53,134		17		(46	)		53,105
Corporate bonds		59,890		3		(129	)		59,764
Mutual funds, held in rabbi trust		10,827		20		(54	)		10,793
		123,851		40		(229	)		123,662
	$	298,635	$	52	$	(330	)	$	298,357

As of January 31, 2020
Short-term Investments:
Municipal and pre-refunded municipal bonds	$	38,617	$	20	$	(11	)	$	38,626
Corporate bonds		166,790		318		(26	)		167,082
Commercial paper		1,997		—		—			1,997
Federal government agencies		1,152		3		—			1,155
Certificate of deposit		2,593		—		—			2,593
		211,149		341		(37	)		211,453
Long-term Investments:
Municipal and pre-refunded municipal bonds		30,340		35		(17	)		30,358
Corporate bonds		47,352		205		(40	)		47,517
Mutual funds, held in rabbi trust		8,448		36		(55	)		8,429
Federal government agencies		6,926		1		(2	)		6,925
Certificates of deposit		3,867		—		—			3,867
		96,933		277		(114	)		97,096
	$	308,082	$	618	$	(151	)	$	308,549

Gross Unrealized Losses and Fair Value of Marketable Securities

The following tables show the gross unrealized losses and fair value of the Company’s marketable securities with unrealized losses that are not deemed to have credit losses, aggregated by the length of time that individual securities have been in a continuous unrealized loss position, at January 31, 2021 and 2020, respectively.

	January 31, 2021
	Less Than 12 Months					12 Months or Greater				Total
Description of Securities	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Municipal and pre-refunded municipal bonds	$	90,308	$	(99	)	$	—	$	—	$	90,308	$	(99	)
Corporate bonds		91,432		(177	)		—		—		91,432		(177	)
Mutual funds, held in rabbi trust		10,793		(54	)		—		—		10,793		(54	)
Total	$	192,533	$	(330	)	$	—	$	—	$	192,533	$	(330	)

	January 31, 2020
	Less Than 12 Months					12 Months or Greater				Total
Description of Securities	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Municipal and pre-refunded municipal bonds	$	24,975	$	(28	)	$	—	$	—	$	24,975	$	(28	)
Corporate bonds		60,067		(66	)		—		—		60,067		(66	)
Mutual funds, held in rabbi trust		5,395		(55	)		—		—		5,395		(55	)
Federal government agencies		3,009		(2	)		—		—		3,009		(2	)
Total	$	93,446	$	(151	)	$	—	$	—	$	93,446	$	(151	)