Segment Reporting (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) segment	Sep. 30, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment			2
Revenues, less transaction-based expenses	$ 1,143	$ 1,078	$ 3,485	$ 3,361
Operating expenses	547	604	1,698	1,752
Operating income	596	474	1,787	1,609
Trading and Clearing Segment
Segment Reporting Information [Line Items]
Revenues, less transaction-based expenses	523	483	1,611	1,584
Operating expenses	213	245	643	672
Operating income	310	238	968	912
Data and Listings Segment
Segment Reporting Information [Line Items]
Revenues, less transaction-based expenses	620	595	1,874	1,777
Operating expenses	334	359	1,055	1,080
Operating income	$ 286	$ 236	$ 819	$ 697
Customer Concentration Risk | Sales Revenue, Segment | One Clearing
Segment Reporting Information [Line Items]
Concentration risk, percentage	10.00%		10.00%	10.00%