Employee Benefit Plans (401(k) and Defined Contribution Pension Plans) (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Morgan Stanley 401(k) Plan | |||
| Defined Contribution Plans | |||
| Descriptions of plan | For 2018, 2017 and 2016, the Firm matched employee contributions up to 4% of eligible pay, up to the IRS limit. | ||
| Maximum percent of employer matching contributions | 4.00% | 4.00% | 4.00% |
| Expense | $ 272 | $ 258 | $ 250 |
| Morgan Stanley 401(k) Plan | Eligible U.S. Employees with Eligible Pay Less than or Equal to $100,000 | |||
| Defined Contribution Plans | |||
| Percent of employer matching contribution of eligible pay | 2.00% | ||
| Non-U.S. Defined Contribution Pension Plans | |||
| Defined Contribution Plans | |||
| Expense | $ 116 | $ 106 | $ 101 |