Acquisitions (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jan. 31, 2019	Oct. 31, 2019	Oct. 31, 2018	Apr. 30, 2020	Oct. 31, 2014
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%		8.20%
Amount paid for indirect profit interest pursuant to the put and call provisions of the Long-term Equity Incentive Plan		$ 7.8	$ 8.2
Estimated fair value of noncontrolling interests		$ 25.2		$ 20.6
Parametric Portfolio Associates [Member] | Parametric Risk Advisors [Member]
Business Acquisition [Line Items]
Purchase of non-controlling direct profit interests	$ 4.0
Noncontrolling capital and profits interest issued in acquisition					20.00%
Noncontrolling Indirect Profit Interest Acquired In Exchange		0.00%		0.00%	0.80%
Noncontrolling Indirect Capital Interest Acquired In Exchange					0.80%
Parametric Portfolio Associates [Member] | Parametric Plan [Member]
Business Acquisition [Line Items]
Total Non-controlling profits interests (direct and indirect) held by interest holders at the end of period		0.00%		0.00%
Amount paid for indirect profit interest pursuant to the put and call provisions of the Long-term Equity Incentive Plan		$ 0.6	$ 5.9