Goodwill and Purchased Intangible Assets (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Jun. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Goodwill [Line Items]
Goodwill expected to be deductible in future periods	$ 895				$ 895
Amortization expense for purchased finite-lived intangible assets	18		13		44	39
Non-cash intangible asset impairment charges		10		28
Technology [Member]
Goodwill [Line Items]
Non-cash intangible asset impairment charges				19
Customer relationships [Member]
Goodwill [Line Items]
Non-cash intangible asset impairment charges		7		6
Trade Names [Member]
Goodwill [Line Items]
Non-cash intangible asset impairment charges		3		3
Market Services [Member]
Goodwill [Line Items]
Non-cash intangible asset impairment charges				17
Technology Solutions [Member]
Goodwill [Line Items]
Non-cash intangible asset impairment charges				11
eSpeed [Member]
Goodwill [Line Items]
Goodwill expected to be deductible in future periods	510				510
TR Businesses [Member]
Goodwill [Line Items]
Goodwill expected to be deductible in future periods	$ 304				$ 304