v3.5.0.2
Segment Reporting (Narrative) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2016
Jun. 30, 2015
Jun. 30, 2016
Jun. 30, 2015
Dec. 31, 2015
Segment Reporting Information [Line Items]          
Total revenues, less transaction-based expenses $ 1,129 $ 797 $ 2,283 $ 1,647  
Operating income 551 430 1,135 892  
Total operating expenses 578 367 1,148 755  
Net income 363 289 740 612 $ 1,295
Trading and Clearing Segment [Member]          
Segment Reporting Information [Line Items]          
Total revenues, less transaction-based expenses 527 491 1,101 1,040  
Operating income 313 272 674 595  
Total operating expenses 214 219 427 445  
Data and Listings Segments [Member]          
Segment Reporting Information [Line Items]          
Total revenues, less transaction-based expenses 602 306 1,182 607  
Operating income 238 158 461 297  
Total operating expenses $ 364 $ 148 $ 721 $ 310