Acquisitions, Goodwill and Intangible Assets (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Oct. 31, 2017	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2014	Oct. 31, 2013
Business Acquisition [Line Items]
Goodwill impairment				$ 0	$ 0	$ 0
Intangible assets amortization expense				5,000	8,900	9,000
Impairment of amortization or non-amortizing intangible assets				0	0	0
Goodwill				$ 259,681	$ 259,681
Parametric Risk Advisors [Member] | Parametric Portfolio Associates [Member]
Business Acquisition [Line Items]
Total percentage of Non-controlling profit and capital interest held by interest holders at the end of period				0.60%	0.60%
Atlanta Capital [Member]
Business Acquisition [Line Items]
Total Non-controlling profits interests (direct and indirect) held by interest holders at the end of period				8.20%	9.80%
Amount paid for indirect profit interest pursuant to the put and call provisions of the Long-term Equity Incentive Plan				$ 7,800	$ 8,200	4,200
Payments for purchase of non-controlling direct profit interests		$ 2,500	$ 700			3,200
Estimated fair value of noncontrolling interests				$ 25,200	26,300
Parametric Portfolio Associates [Member]
Business Acquisition [Line Items]
Total Non-controlling profits interests (direct and indirect) held by interest holders at the end of period				5.10%
Estimated fair value of noncontrolling interests					63,800
Accelerated Repurchases, Amount				$ 73,500
Total capital interest held by non-controlling interest holders				0.80%
Parametric Portfolio Associates [Member] | Parametric Risk Advisors [Member]
Business Acquisition [Line Items]
Purchase of non-controlling direct profit interests	$ 4,000
Estimated fair value of noncontrolling interests				$ 12,300
Noncontrolling capital and profits interest issued in acquisition							20.00%
Noncontrolling Indirect Profit Interest Acquired In Exchange	0.20%						0.80%
Noncontrolling Indirect Capital Interest Acquired In Exchange	0.20%						0.80%
Parametric Portfolio Associates [Member] | Clifton Group [Member]
Business Acquisition [Line Items]
Company's increase in capital interest percentage under acquisition agreement, during the period		0.50%
Company's increase in profit interest percentage under acquisition agreement, during the period		0.50%
Purchase of non-controlling direct profit interests					8,400	6,900
Noncontrolling Indirect Profit Interest Acquired In Exchange								1.90%
Noncontrolling Indirect Capital Interest Acquired In Exchange								1.90%
Parametric Portfolio Associates [Member] | Parametric Plan [Member]
Business Acquisition [Line Items]
Amount paid for indirect profit interest pursuant to the put and call provisions of the Long-term Equity Incentive Plan				600	$ 5,900	5,700
Estimated fair value of noncontrolling interests				$ 61,200
Tax Advantaged Bond Strategies [Member]
Business Acquisition [Line Items]
Goodwill, Acquired During Period						$ 11,600