Fair Value Measurements Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Nov. 13, 2013	Nov. 30, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes				$ 400
Equity Method Investments, Fair Value Disclosure	374		4
Fair Value Assets Measured On Recurring Basis Equity Method And Cost Method Investments	53	172
Long-term investment in equity securities	379	324
U.S. Treasury securities	374	100
Mutual Funds	27	33
Foreign Currency Contract, Asset, Fair Value Disclosure		4
Total assets at fair value	780	461
Income (Loss) from Equity Method Investments	26
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	25
Equity Method Investment, Reduction to Income, Transaction Based Expenses	1
Potential Equity Capital	150
Fair Value Assumptions, Expected Dividend Rate	50.00%
Committed Equity Capital Contribution	200
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Method Investments, Fair Value Disclosure		100
Long-term investment in equity securities	379	324
U.S. Treasury securities	374	100
Mutual Funds	27	33
Foreign Currency Contract, Asset, Fair Value Disclosure		0
Total assets at fair value	780	457
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term investment in equity securities	0	0
U.S. Treasury securities	0	0
Mutual Funds	0	0
Foreign Currency Contract, Asset, Fair Value Disclosure		4
Total assets at fair value	0	4
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term investment in equity securities	0	0
U.S. Treasury securities	0	0
Mutual Funds	0	0
Foreign Currency Contract, Asset, Fair Value Disclosure		0
Total assets at fair value	0	0
Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes	1,390
Debt Instrument, Fair Value Disclosure	1,460
NYSE Euronext USD Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes	1,990
Debt Instrument, Fair Value Disclosure	2,010		854
Options Clearing Corporation [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Method Investment, Ownership Percentage			40.00%
NYSE [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Potential Equity Capital	60
Committed Equity Capital Contribution	$ 80
Cetip, S.A. [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Method Investment, Ownership Percentage	12.00%