Short-Term and Long-Term Investments - Components of Investments (Details) - USD ($) $ in Thousands	Jan. 31, 2020	Oct. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 120,035
Estimated Fair Value	120,143
U.S. government obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	120,035	$ 119,732
Gross Unrealized Gains	108	225
Gross Unrealized Losses	0	(3)
Estimated Fair Value	120,143	119,954
Included in short-term investments | U.S. government obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	109,962	109,715
Gross Unrealized Gains	105	225
Gross Unrealized Losses	0	0
Estimated Fair Value	110,067	109,940
Included in long-term investments | U.S. government obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	10,073	10,017
Gross Unrealized Gains	3	0
Gross Unrealized Losses	0	(3)
Estimated Fair Value	$ 10,076	$ 10,014