Acquisitions (Purchase Price Allocation) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015	Dec. 14, 2015	Dec. 11, 2015
Business Acquisition [Line Items]
Goodwill	$ 12,009	$ 12,079
TRAYPORT [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill				$ 274
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net				8
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities				(50)
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net				620
Goodwill				$ 388
Interactive Data Holdings Corporation Acquisition [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents			$ 301
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill			2,883
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net			273
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities			(1,057)
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net			5,628
Goodwill			$ 3,228