v3.5.0.2
Segment Reporting (Narrative) (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Dec. 31, 2015
Segment Reporting Information [Line Items]          
Total revenues, less transaction-based expenses $ 1,078 $ 816 $ 3,361 $ 2,463  
Operating income 474 440 1,609 1,332  
Total operating expenses 604 376 1,752 1,131  
Net income 350 310 1,090 922 $ 1,295
Trading and Clearing Segment [Member]          
Segment Reporting Information [Line Items]          
Total revenues, less transaction-based expenses 483 506 1,584 1,546  
Operating income 238 277 912 872  
Total operating expenses 245 229 672 674  
Data and Listings Segments [Member]          
Segment Reporting Information [Line Items]          
Total revenues, less transaction-based expenses 595 310 1,777 917  
Operating income 236 163 697 460  
Total operating expenses $ 359 $ 147 $ 1,080 $ 457