Subsequent Events (Details) (USD $) In Millions, unless otherwise specified		0 Months Ended							3 Months Ended
	Mar. 31, 2013 sqft	Apr. 05, 2013 Subsequent event MBS & Rates and Credit Products item	Apr. 05, 2013 Subsequent event MBS & Rates and Credit Products Minimum	Apr. 05, 2013 Subsequent event MBS & Rates and Credit Products Maximum	Apr. 05, 2013 Subsequent event MBS & Rates and Credit Products Severance and other compensation Minimum	Apr. 05, 2013 Subsequent event MBS & Rates and Credit Products Severance and other compensation Maximum	Apr. 05, 2013 Subsequent event MBS & Rates and Credit Products Third party vendor contracts Minimum	Apr. 05, 2013 Subsequent event MBS & Rates and Credit Products Third party vendor contracts Maximum	Jun. 30, 2013 Subsequent event Segment, MBS & Rates Minimum	Jun. 30, 2013 Subsequent event Segment, MBS & Rates Maximum
Subsequent Events
Number of employees who could be impacted		160
Expected total charge in connection with the plan to discontinue operations			$ 15	$ 20	$ 11	$ 13	$ 4	$ 7
Future cash expenditures			11	16
Area of headquarters (in square feet)	84,000
Average cost (in dollars per square foot)	62
Estimated net trading losses expected to be recognized									$ 3.0	$ 4.0