|
Equity Method Investments (Narratives) (Details)
In Millions, unless otherwise specified |
3 Months Ended | 6 Months Ended | 0 Months Ended | 3 Months Ended | 4 Months Ended | 6 Months Ended | 3 Months Ended | 3 Months Ended | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Jun. 30, 2012
USD ($)
|
Jun. 30, 2011
USD ($)
|
Jun. 30, 2012
USD ($)
|
Jun. 30, 2011
USD ($)
|
Dec. 31, 2011
USD ($)
|
May 01, 2010
MUMSS
USD ($)
|
May 01, 2010
MUMSS
JPY (¥)
|
Jun. 30, 2012
MUMSS
USD ($)
|
Jun. 30, 2011
MUMSS
USD ($)
|
Apr. 22, 2011
MUMSS
USD ($)
|
Jun. 30, 2012
MUMSS
USD ($)
|
Jun. 30, 2011
MUMSS
USD ($)
|
Jun. 30, 2011
MSMS
USD ($)
|
May 01, 2010
MSMS
|
Jun. 30, 2011
FrontPoint
USD ($)
|
Jun. 30, 2011
Morgan Stanley Huaxin Securities Company Limited
USD ($)
|
|
| Schedule of Equity Method Investments [Line Items] | ||||||||||||||||
| Equity method investment | $ 4,428 | $ 4,428 | $ 4,524 | |||||||||||||
| Income (loss) from equity method investments | 12 | (65) | (20) | (725) | 54 | (17) | 81 | (672) | (20) | |||||||
| Percent ownership | 40.00% | |||||||||||||||
| Cash contribution received from partner(s) of the joint venture | 247 | 23,000 | ||||||||||||||
| Economic interest held by joint venture partners | 60.00% | 60.00% | ||||||||||||||
| Voting interest in joint venture | 40.00% | 40.00% | 51.00% | |||||||||||||
| Voting interest held by noncontrolling interest | 60.00% | 60.00% | 49.00% | |||||||||||||
| Proceeds from transfer of risk associated with fixed income trading positions | 659 | |||||||||||||||
| Capital injection by joint venture partner due to losses | 370 | |||||||||||||||
| Increase in carrying amount of the equity method investment | 148 | |||||||||||||||
| Share of increase in the net asset value, percent | 40.00% | |||||||||||||||
| Increase to paid-in capital | 86 | |||||||||||||||
| Payments to acquire interest in joint venture | $ 130 | |||||||||||||||