v3.10.0.1
Deferred Compensation Plans (Performance-Based Stock Units) (Details) - PSUs - $ / shares
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Share-based Payment Awards      
Terms of award PSUs will vest and convert to shares of common stock only if the Firm satisfies predetermined performance and market-based conditions over a three-year performance period.    
Non-option awards outstanding (shares) 3,000,000    
Minimum      
Share-based Payment Awards      
Percentage of PSUs that vested 0.00%    
Maximum      
Share-based Payment Awards      
Percentage of PSUs that vested 150.00%    
MS Adjusted ROE      
Share-based Payment Awards      
Fair value per PSU on award date $ 56.84 $ 42.64 $ 25.19
Relative MS TSR      
Share-based Payment Awards      
Fair value per PSU on award date $ 65.81 $ 48.02 $ 24.51