Acquisitions 1 (Details) - USD ($) $ in Millions	3 Months Ended					6 Months Ended
	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jan. 31, 2016	Apr. 30, 2017
Atlanta Capital [Member]
Business Acquisition Contingent Consideration [Line Items]
Company's increase in profit interest percentage under acquisition agreement, during the period		0.10%
Non-controlling interest holders total (direct and indirect) profits interest, end of period		13.10%		13.00%		13.10%
Profit interest granted to non-controlling interest holders under the Long-term Equity Incentive Plan			1.10%
Company's increase in indirect profit interest percentage under Long-term Equity Incentive Plan, during the period				0.90%
Purchase of non-controlling interests	$ 0.4
Amount paid for indirect profit interest pursuant to the put and call provisions of the Long-term Equity Incentive Plan			$ 1.9
Parametric Portfolio Associates [Member]
Business Acquisition Contingent Consideration [Line Items]
Company's increase in capital interest percentage under acquisition agreement, during the period			0.50%		0.50%
Company's increase in profit interest percentage under acquisition agreement, during the period			0.50%		0.50%
Non-controlling interest holders capital ownership percentage, end of period		1.30%		1.80%		1.30%
Non-controlling interest holders total (direct and indirect) profits interest, end of period		6.40%		7.00%		6.40%
Company's increase in indirect profit interest percentage under Long-term Equity Incentive Plan, during the period				0.10%
Purchase of non-controlling interests			$ 6.9
Amount paid for indirect profit interest pursuant to the put and call provisions of the Long-term Equity Incentive Plan			$ 0.6
Parametric Portfolio Associates [Member] | Call Option [Member]
Business Acquisition Contingent Consideration [Line Items]
Purchase of non-controlling interests					$ 2.1
Parametric Portfolio Associates [Member] | Put Option [Member]
Business Acquisition Contingent Consideration [Line Items]
Purchase of non-controlling interests					$ 4.1
Tax Advantaged Bond Strategies [Member]
Business Acquisition Contingent Consideration [Line Items]
Goodwill acquired						$ 11.6