Short-Term and Long-Term Investments (Details) - USD ($) $ in Thousands	Jul. 31, 2018	Oct. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 258,894
U.S. government obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	228,953	$ 299,408
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(491)	(432)
Estimated Fair Value	228,462	298,976
U.S. government obligations \| Included in short-term investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	199,415	249,498
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(418)	(305)
Estimated Fair Value	198,997	249,193
U.S. government obligations \| Included in long-term investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	29,538	49,910
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(73)	(127)
Estimated Fair Value	29,465	49,783
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	29,941	29,939
Gross Unrealized Gains	2	1
Gross Unrealized Losses	0	0
Estimated Fair Value	29,943	29,940
Commercial paper \| Included in short-term investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	29,941	29,939
Gross Unrealized Gains	2	1
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 29,943	$ 29,940

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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-Topic 320
-SubTopic 10
-Section 50
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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).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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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).

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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