Revenue (Summary of Management fee revenue by investment mandate) (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]
Revenue	$ 452,554	$ 406,416
Total Management Fees [Member]
Disaggregation of Revenue by Source [Line Items]
Revenue	394,801	350,750
Management Fees: Equity [Member]
Disaggregation of Revenue by Source [Line Items]
Revenue	195,754	163,897
Management Fees: Fixed Income [Member]
Disaggregation of Revenue by Source [Line Items]
Revenue	65,503	58,007
Management Fees: Floating-Rate Income [Member]
Disaggregation of Revenue by Source [Line Items]
Revenue	43,060	53,678
Management Fees: Alternative [Member]
Disaggregation of Revenue by Source [Line Items]
Revenue	13,735	16,173
Management Fees: Parametric Custome Portfolios [Member]
Disaggregation of Revenue by Source [Line Items]
Revenue	64,982	48,907
Management Fees: Parametric Custome Portfolios [Member] | Restatement Adjustment [Member]
Disaggregation of Revenue by Source [Line Items]
Revenue		9,000
Management Fees: Parametric Overlay Services [Member]
Disaggregation of Revenue by Source [Line Items]
Revenue	$ 11,767	$ 10,088