Software Development and Intellectual Property Licenses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Software development and intellectual property licenses:
Internally-developed software costs	$ 232		$ 232		$ 277
Payments made to third-party software developers	221		221		189
Total software development costs	453		453		$ 466
Amortization:
Amortization of capitalized software development costs and intellectual property licenses	$ 79	$ 81	$ 172	$ 213