Intangible Assets And Goodwill (Components Of Intangible Assets) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets	$ 2,879.5		$ 3,312.8
Other Indefinite-lived Intangible Assets	17,040.5	[1]	17,040.5	[1]
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets	450.0		578.0
Foreign Currency Translation Adjustments [Member]
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets	0		(0.4)
Clearing Firm, Market Data And Other Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	2,838.7		3,071.9
Accumulated amortization	(443.4)		(400.4)
Net book value	2,395.3		2,671.5
Lease-Related Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	47.2		83.2
Accumulated amortization	(29.5)		(45.4)
Net book value	17.7		37.8
Technology-Related Intellectual Property [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	29.4		56.2
Accumulated amortization	(12.9)		(28.4)
Net book value	16.5		27.8
Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	9.8	[2]	11.6	[2]
Accumulated amortization	(9.8)	[2]	(10.6)	[2]
Net book value	0	[2]	1.0	[2]
Total Amortizable Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	2,925.1		3,222.9
Accumulated amortization	(495.6)		(484.8)
Net book value	2,429.5		2,738.1
Foreign Currency Translation Adjustments [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	0		(8.8)
Accumulated amortization	0		5.9
Net book value	0		(2.9)
Total Amortizable Intangible Assets, Net [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	2,925.1		3,214.1
Accumulated amortization	(495.6)		(478.9)
Net book value	$ 2,429.5		$ 2,735.2

[1] Trading products represent futures and options products acquired in our business combinations with CBOT Holdings, Inc. (CBOT Holdings) and NYMEX Holdings, Inc. (NYMEX Holdings). Clearing and transaction fees revenues are generated through the trading of these products. These trading products, most of which have traded for decades, require authorization from the Commodity and Futures Trading Commission (CFTC). Product authorizations from the CFTC have no term limits.

[2] At September 30, 2012, other amortizable intangible assets consisted of market maker agreements and a definite-lived trade name. At December 31, 2011, other amortizable intangible assets consisted of service and market maker agreements and a definite-lived trade name.