Short-Term and Long-Term Investments (Details) - USD ($) $ in Thousands	Jul. 31, 2019	Oct. 31, 2018
U.S. government obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 119,490	$ 198,394
Gross Unrealized Gains	180	0
Gross Unrealized Losses	0	(406)
Estimated Fair Value	119,670	197,988
U.S. government obligations \| Included in short-term investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	119,490	139,365
Gross Unrealized Gains	180	0
Gross Unrealized Losses	0	(347)
Estimated Fair Value	$ 119,670	139,018
U.S. government obligations \| Included in long-term investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		59,029
Gross Unrealized Gains		0
Gross Unrealized Losses		(59)
Estimated Fair Value		58,970
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
Commercial paper \| Included in short-term investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		9,963
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Estimated Fair Value		$ 9,963

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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Amount, before tax, of unrealized loss 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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Amortized cost of 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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