Investments - Available-for-Sale Marketable Securities, Fair Value and Unrealized Losses Continuous Unrealized Loss Position (Details) $ in Thousands	Apr. 30, 2020 USD ($)
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
AFS, Less Than 12 Months, Unrealized Losses	$ (26)
AFS, Less Than 12 Months, Fair Value	44,411
AFS, 12 Months or Greater, Unrealized Losses	0
AFS, 12 Months or Greater, Fair Value	0
AFS, Total Unrealized Losses	(26)
AFS, Total Fair Value	44,411
U.S. treasury securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
AFS, Less Than 12 Months, Unrealized Losses	0
AFS, Less Than 12 Months, Fair Value	0
AFS, 12 Months or Greater, Unrealized Losses	0
AFS, 12 Months or Greater, Fair Value	0
AFS, Total Unrealized Losses	0
AFS, Total Fair Value	0
U.S. government agencies securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
AFS, Less Than 12 Months, Unrealized Losses	0
AFS, Less Than 12 Months, Fair Value	0
AFS, 12 Months or Greater, Unrealized Losses	0
AFS, 12 Months or Greater, Fair Value	0
AFS, Total Unrealized Losses	0
AFS, Total Fair Value	0
Certificate of deposit
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
AFS, Less Than 12 Months, Unrealized Losses	(7)
AFS, Less Than 12 Months, Fair Value	10,995
AFS, 12 Months or Greater, Unrealized Losses	0
AFS, 12 Months or Greater, Fair Value	0
AFS, Total Unrealized Losses	(7)
AFS, Total Fair Value	10,995
Commercial paper
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
AFS, Less Than 12 Months, Unrealized Losses	(5)
AFS, Less Than 12 Months, Fair Value	18,495
AFS, 12 Months or Greater, Unrealized Losses	0
AFS, 12 Months or Greater, Fair Value	0
AFS, Total Unrealized Losses	(5)
AFS, Total Fair Value	18,495
Corporate debt securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
AFS, Less Than 12 Months, Unrealized Losses	(14)
AFS, Less Than 12 Months, Fair Value	14,921
AFS, 12 Months or Greater, Unrealized Losses	0
AFS, 12 Months or Greater, Fair Value	0
AFS, Total Unrealized Losses	(14)
AFS, Total Fair Value	$ 14,921

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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