Common Stock (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
	Dec. 18, 2020	Oct. 31, 2020	Oct. 31, 2019	Nov. 23, 2020
Equity, Class of Treasury Stock [Line Items]
Special dividends payable amount per share				$ 4.25
Morgan Stanley [Member] | Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Special dividends paid	$ 494.9
Voting Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Stock issued during period		55,708
Repurchase of Common Stock (shares)		13,927
Non-Voting Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Amount of non-voting common stock shares authorized by the Company's Board of Directors to be repurchased and retired under the current share repurchase plan		8,000,000.0
Date on which the current Non-Voting Common Stock share repurchase program was announced		Jul. 10, 2019
Repurchase of Common Stock (shares)			7,409,000
Non-Voting Common Stock [Member] | Morgan Stanley [Member] | Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Special dividends payable amount per share				$ 4.25
Non-Voting Common Stock Current Repurchase Authorization [Member]
Equity, Class of Treasury Stock [Line Items]
Non-voting common stock shares repurchased and retired under the Company's current share repurchase plan during the period		4,200,000