Financial Assets and Liabilities - Short-term investments (Details) - Cash equivalents - USD ($) $ in Thousands	Apr. 30, 2020		Oct. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, cost	$ 168,653		$ 166,024
Gross unrealized gains	0		0
Gross unrealized losses less than 12 months	0		0
Gross unrealized losses 12 months or longer	0		0
Estimated fair value	168,653	[1]	166,024	[2]
Money market funds
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, cost	168,653		166,024
Gross unrealized gains	0		0
Gross unrealized losses less than 12 months	0		0
Gross unrealized losses 12 months or longer	0		0
Estimated fair value	$ 168,653	[1]	$ 166,024	[2]

[1] See Note 7. Fair Value Measures for further discussion on fair values of cash equivalents.

[2] See Note 7. Fair Value Measures for further discussion on fair values of cash equivalents.