Revenue (Summary of Total Revenue by Source) (Details) - Accounting Standards Update 2014-09 [Member] - USD ($) $ in Thousands	3 Months Ended
	Jan. 31, 2020	Jan. 31, 2019
Disaggregation of Revenue by Source [Line Items]
Total revenue	$ 452,554	$ 406,416
Management Fees: Sponsored Funds [Member]
Disaggregation of Revenue by Source [Line Items]
Total revenue	266,290	242,666
Management Fees: Seperate Accounts [Member]
Disaggregation of Revenue by Source [Line Items]
Total revenue	128,511	108,084
Total Management Fees [Member]
Disaggregation of Revenue by Source [Line Items]
Total revenue	394,801	350,750
Distribution And Underwriter Fees: Distribution Fees [Member]
Disaggregation of Revenue by Source [Line Items]
Total revenue	15,064	19,045
Distribution And Underwriter Fees: Underwriter Commissions [Member]
Disaggregation of Revenue by Source [Line Items]
Total revenue	6,514	4,045
Total Distribution And Underwriter Fees [Member]
Disaggregation of Revenue by Source [Line Items]
Total revenue	21,578	23,090
Service Fees [Member]
Disaggregation of Revenue by Source [Line Items]
Total revenue	33,939	29,360
Other Revenue [Member]
Disaggregation of Revenue by Source [Line Items]
Total revenue	$ 2,236	$ 3,216