Financial Instruments - (Tables)

9 Months Ended

Oct. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Cash Equivalents, Marketable Securities and Restricted Cash

The following tables summarize our cash equivalents, marketable securities and restricted cash by significant investment categories as of January 31, 2019 and October 31, 2019 (in thousands):

	As of January 31, 2019
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value		Cash Equivalents		Marketable Securities		Restricted Cash
Level 1
Money market accounts	$	—	$	—	$	—	$	43,038	$	27,215	$	—	$	15,823
Level 2
U.S. government treasury notes	315,329		208		(315)		315,222		34,129		281,093		—
U.S. government agencies	69,114		17		(154)		68,977		9,983		58,994		—
Corporate debt securities	363,860		534		(757)		363,637		—		363,637		—
Foreign government bonds	7,965		36		—		8,001		—		8,001		—
Asset-backed securities	37,664		105		(12)		37,757		—		37,757		—
Total	$	793,932	$	900	$	(1,238)	$	836,632	$	71,327	$	749,482	$	15,823

	As of October 31, 2019
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value		Cash Equivalents		Marketable Securities		Restricted Cash
Level 1
Money market accounts	$	—	$	—	$	—	$	20,372	$	5,085	$	—	$	15,287
Level 2
U.S. government treasury notes	350,325		2,165		(30)		352,460		—		352,460		—
U.S. government agencies	42,120		331		(1)		42,450		—		42,450		—
Corporate debt securities	436,842		3,800		(10)		440,632		2,361		438,271		—
Foreign government bonds	14,988		131		(5)		15,114		—		15,114		—
Asset-backed securities	88,222		466		(14)		88,674		—		88,674		—
Total	$	932,497	$	6,893	$	(60)	$	959,702	$	7,446	$	936,969	$	15,287

Amortized Cost and Estimated Fair Value

The amortized cost and estimated fair value of our marketable securities are shown below by contractual maturity (in thousands):

	As of October 31, 2019
	Amortized Cost		Fair Value
Due within one year	$	427,200	$	429,154
Due in one to five years	502,936		507,815
Total	$	930,136	$	936,969

Gross Unrealized Losses and Fair Values

The following table presents gross unrealized losses and fair values for those investments that were in a continuous unrealized loss position as of October 31, 2019, aggregated by investment category (in thousands):

	Less than 12 months				Greater than 12 months				Total
	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
U.S. government treasury notes	$	23,968	$	(27)	$	3,623	$	(3)	$	27,591	$	(30)
U.S. government agencies	—		—		1,938		(1)		1,938		(1)
Corporate debt securities	11,532		(7)		10,366		(3)		21,898		(10)
Foreign government bonds	2,964		(5)		—		—		2,964		(5)
Asset-backed securities	16,130		(14)		—		—		16,130		(14)
Total	$	54,594	$	(53)	$	15,927	$	(7)	$	70,521	$	(60)