Regulatory Requirements (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
MS&Co.
Regulatory Requirements
Net capital	$ 9,533	$ 6,593
Amount of capital that exceeds the minimum required	7,784	4,928
Net capital, minimum amount required to hold	1,000
Net capital, minimum amount required to hold in accordance with the market and credit risk standards	500
MS&Co. | Minimum
Regulatory Requirements
Amount by which if net capital falls below, the company is required to notify the SEC	5,000
MSSB LLC
Regulatory Requirements
Net capital	4,452	4,620
Amount of capital that exceeds the minimum required	$ 4,295	$ 4,460