Commitments, Contingencies And Guarantees (Details) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2011	Dec. 31, 2010
Loss Contingencies [Line Items]
Credit facility used	$ 0
Other guarantees	18,000,000	24,000,000
Securities held as collateral, at fair value	8,000,000	8,000,000
Escrow agreements	22,000,000
Performance Guarantee [Member]
Loss Contingencies [Line Items]
Other guarantees	6,000,000
Wholly-Owned Subsidiary [Member]
Loss Contingencies [Line Items]
Other guarantees	25,000,000
Cash collateral for borrowed securities	18,000,000	15,000,000
Brokerage Activities [Member]
Loss Contingencies [Line Items]
Contingent liability	0
Clearinghouse Credit Facilities [Member]
Loss Contingencies [Line Items]
Total credit facility	5,000,000
Credit facilities, total	433,000,000	440,000,000
Line of credit facility, available liquidity	192,000,000	196,000,000
Credit facility, regulatory requirements amount	241,000,000	244,000,000
Contingent liability	0
NASDAQ OMX Commodities And NASDAQ OMX Stockholm [Member]
Loss Contingencies [Line Items]
Customer collateral pledged to NASDAQ OMX in event of customer default	$ 5,800,000,000	$ 8,700,000,000