Fair Value Measurements (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unsecured Long-term Debt, Noncurrent		$ 852
Long-term investment in equity securities	$ 416	299
U.S. Treasury securities	503	449
Mutual Funds	24	29
Total assets at fair value	943	777
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term investment in equity securities	416	299
Mutual Funds	24	29
Total assets at fair value	943	777
Narrative [Abstract]
Equity method investments, fair value	503	449
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
Total assets at fair value	0	0
Cash and Cash Equivalents [Member]
Narrative [Abstract]
Equity method investments, fair value	1
Restricted Cash And Investments [Member]
Narrative [Abstract]
Equity method investments, fair value	352
Restricted Cash and Investments, Non Current [Member]
Narrative [Abstract]
Equity method investments, fair value	150
Two Thousand Twenty Senior Notes [Member]
Narrative [Abstract]
Fair value of senior notes	1,300
Senior Notes [Member]
Narrative [Abstract]
Fair value of senior notes	1,360
NYSE Euronext USD Notes [Member]
Narrative [Abstract]
Fair value of senior notes	857
Cetip, S.A. [Member]
Narrative [Abstract]
Available-for-sale Securities, Equity Securities	416
Available-for-sale Securities, Gross Unrealized Gain (Loss)	91
Two Thousand Twenty Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unsecured Long-term Debt, Noncurrent	1,241	789
Two Thousand Twenty Three Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unsecured Long-term Debt, Noncurrent	790	1,240
Narrative [Abstract]
Fair value of senior notes	882
Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unsecured Long-term Debt, Noncurrent	1,241
NYSE Euronext USD Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unsecured Long-term Debt, Noncurrent	851	597
Two Thousand Eighteen Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unsecured Long-term Debt, Noncurrent	597	$ 1,239
Narrative [Abstract]
Fair value of senior notes	$ 615
Cetip, S.A. [Member]
Narrative [Abstract]
Business Acquisition, Share Price	$ 45.69