Short-Term and Long-Term Investments (Details) - USD ($) $ in Thousands	Oct. 31, 2019	Oct. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 119,732
Estimated Fair Value	119,954
U.S. government obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	119,732	$ 198,394
Gross Unrealized Gains	225	0
Gross Unrealized Losses	(3)	(406)
Estimated Fair Value	119,954	197,988
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		9,963
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Estimated Fair Value		9,963
Short-term Investments \| U.S. government obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	109,715	139,365
Gross Unrealized Gains	225	0
Gross Unrealized Losses	0	(347)
Estimated Fair Value	109,940	139,018
Short-term Investments \| Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		9,963
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Estimated Fair Value		9,963
Other Long-term Investments \| U.S. government obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	10,017	59,029
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(3)	(59)
Estimated Fair Value	$ 10,014	$ 58,970

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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