Financial Instruments - Gross Unrealized Losses and Fair Values (Details) $ in Thousands	Oct. 31, 2019 USD ($)
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Fair Value, Less than 12 months	$ 54,594
Unrealized Loss, Less than 12 Months	(53)
Fair Value, Greater than 12 months	15,927
Unrealized Loss, Greater than 12 months	(7)
Fair Value, Total	70,521
Unrealized Loss, Total	(60)
U.S. government treasury notes
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Fair Value, Less than 12 months	23,968
Unrealized Loss, Less than 12 Months	(27)
Fair Value, Greater than 12 months	3,623
Unrealized Loss, Greater than 12 months	(3)
Fair Value, Total	27,591
Unrealized Loss, Total	(30)
U.S. government agencies
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Fair Value, Less than 12 months	0
Unrealized Loss, Less than 12 Months	0
Fair Value, Greater than 12 months	1,938
Unrealized Loss, Greater than 12 months	(1)
Fair Value, Total	1,938
Unrealized Loss, Total	(1)
Corporate debt securities
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Fair Value, Less than 12 months	11,532
Unrealized Loss, Less than 12 Months	(7)
Fair Value, Greater than 12 months	10,366
Unrealized Loss, Greater than 12 months	(3)
Fair Value, Total	21,898
Unrealized Loss, Total	(10)
Foreign government bonds
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Fair Value, Less than 12 months	2,964
Unrealized Loss, Less than 12 Months	(5)
Fair Value, Greater than 12 months	0
Unrealized Loss, Greater than 12 months	0
Fair Value, Total	2,964
Unrealized Loss, Total	(5)
Asset-backed securities
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Fair Value, Less than 12 months	16,130
Unrealized Loss, Less than 12 Months	(14)
Fair Value, Greater than 12 months	0
Unrealized Loss, Greater than 12 months	0
Fair Value, Total	16,130
Unrealized Loss, Total	$ (14)

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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.

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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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