Deferred Revenue (Estimated Deferred Revenue) (Details) (USD $) In Millions	Sep. 30, 2011
Deferred Revenue Arrangement [Line Items]
2011	$ 82	[1]
2012	88
2013	67
2014	41
2015	20
2016 and thereafter	12
Deferred revenue estimated revenue to be recognized	310
Initial Listing Revenues [Member]
Deferred Revenue Arrangement [Line Items]
2011	4	[1]
2012	13
2013	9
2014	6
2015	5
2016 and thereafter	3
Deferred revenue estimated revenue to be recognized	40
Listing Of Additional Shares Revenues [Member]
Deferred Revenue Arrangement [Line Items]
2011	10	[1]
2012	33
2013	26
2014	14
2015	3
Deferred revenue estimated revenue to be recognized	86
Annual Renewal And Other Revenues [Member]
Deferred Revenue Arrangement [Line Items]
2011	56	[1]
2012	3
Deferred revenue estimated revenue to be recognized	59
Market Technology [Member]
Deferred Revenue Arrangement [Line Items]
2011	12	[1],[2]
2012	39	[2]
2013	32	[2]
2014	21	[2]
2015	12	[2]
2016 and thereafter	9	[2]
Deferred revenue estimated revenue to be recognized	$ 125	[2]

[1] Represents deferred revenue that is anticipated to be recognized over the remaining three months of 2011.

[2] The timing of recognition of our deferred Market Technology revenues is dependent upon the completion of customization and any significant modifications made pursuant to existing contracts. As such, as it relates to these revenues, the timing represents our best estimate.