Acquisitions (Summary Of The Allocation Of The Total Purchase Consideration) (Details) In Millions, unless otherwise specified				1 Months Ended
	Dec. 31, 2010 USD ($)	Dec. 31, 2010 FTEN [Member] USD ($)		Aug. 31, 2010 SMARTS [Member] USD ($)	Mar. 31, 2011 SMARTS [Member] USD ($)	Dec. 31, 2010 SMARTS [Member] USD ($)		Dec. 31, 2010 Nord Pool ASA [Member] USD ($)		May 31, 2010 Nord Pool ASA [Member] USD ($)	May 31, 2010 Nord Pool ASA [Member] NOK
Business Acquisition [Line Items]
Purchase Consideration	$ 204	$ 110	[1]	$ 77		$ 77	[2]	$ 17	[3]	$ 17	101
Total Net (Liabilities) Assets Acquired	1	(1)	[1]	(5)		(5)	[2]	7	[3]	7
Purchased Intangible Assets	76	46	[1]	28		28	[2]	2	[3]
Goodwill	127	65	[1]			54	[2]	8	[3]
SMARTS acquisition initial purchase price				75
Purchase consideration held in escrow		11
Purchase consideration paid out of escrow					2
Purchase consideration to be paid out of escrow in 2012				11
SMARTS acquisition working capital adjustment				2
Total acquired net assets at fair value		3		3						8
Acquisition recorded as current deferred tax liability		2		1
Acquisition recorded as non-current deferred tax liability		16		7
Acquisition recorded as non-current deferred tax asset		14
Total deferred tax liability		18		8						1
Tax basis of intangible asset acquired		0		0
Acquisition effective tax rate		39.55%		30.00%
Acquired intangible asset in technology		12		11
Acquired intangible asset in trade name		9
Acquired intangible asset in non-compete agreements		2
Acquired intangible asset in customer relationships		$ 23		$ 17

[1] In December 2010, we acquired FTEN, Inc., or FTEN, a leading provider of Real-Time Risk Management solutions for the financial securities market for $110 million. FTEN purchase consideration included $11 million held in escrow to be paid in 2012, in accordance with the purchase agreement. We acquired net assets, at fair value, totaling $3 million and recorded a current deferred tax liability of $2 million and a non-current deferred tax liability of $16 million related to purchased intangible assets, and we also recorded a non-current deferred tax asset of $14 million related to net operating loss carry forwards, resulting in total net liabilities acquired of $1 million. The total deferred tax liabilities of $18 million represent the tax effect of the difference between the estimated assigned fair value of the acquired intangible assets ($46 million) and the tax basis ($0) of such assets. The estimated amount of $18 million is determined by multiplying the difference of $46 million by FTEN's effective tax rate of 39.55%. The purchased intangible assets of $46 million consisted of $23 million in customer relationships, $12 million in technology, $9 million for the FTEN trade name and $2 million related to non-compete agreements.

[2] In August 2010, we acquired SMARTS Group Holdings Pty Ltd, or SMARTS, a leading technology provider of surveillance solutions to exchanges, regulators, and brokers to diversify our Market Technology business and enter the broker surveillance and compliance market. We completed our acquisition of SMARTS for $77 million, which included a $75 million initial purchase price, as well as a $2 million working capital adjustment. SMARTS purchase consideration also included $2 million held in escrow that was paid in the first quarter of 2011 and $11 million held in escrow to be paid in 2012, in accordance with the purchase agreement. We acquired net assets, at fair value, totaling $3 million and recorded a current deferred tax liability of $1 million and a non-current deferred tax liability of $7 million related to purchased intangible assets, resulting in total net liabilities acquired of $5 million. The total deferred tax liabilities of $8 million represent the tax effect of the difference between the estimated assigned fair value of the acquired intangible assets ($28 million) and the tax basis ($0) of such assets. The estimated amount of $8 million is determined by multiplying the difference of $28 million by SMARTS' effective tax rate of 30%. The purchased intangible assets of $28 million consisted of $11 million in technology and $17 million in customer relationships.

[3] In May 2010, we acquired Nord Pool, a derivatives trading market, for $17 million (101 million Norwegian Krone). We acquired net assets, at fair value, totaling $8 million and recorded a non-current deferred tax liability of $1 million related to purchased intangible assets, resulting in total net assets acquired of $7 million. Through this acquisition, we now hold a Norwegian exchange license and operate the Nordic power market and the European carbon market on one trading platform.