Significant Accounting Policies - Adjustments for New Accounting Pronouncements (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended	12 Months Ended
	Apr. 30, 2017	Jan. 31, 2017	Jul. 31, 2017	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reduction of income tax expense	$ 72	$ 852	$ 952	$ 3,345	$ 0	$ 0
Net cash provided by (used in) operating activities				408,953	296,759	300,436
Net cash provided by (used in) financing activities				$ 57,864	58,903	111,946
Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by (used in) operating activities					3,900	2,600
Net cash provided by (used in) financing activities					$ 3,900	$ 2,600
Accounting Standards Update 2016-09 | Paid-in Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption		$ 676