Software Development and Intellectual Property Licenses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Software development and intellectual property licenses:
Internally-developed software costs	$ 266		$ 266		$ 277
Payments made to third-party software developers	225		225		189
Total software development costs	491		491		$ 466
Amortization:
Amortization of capitalized software development costs and intellectual property licenses	$ 34	$ 47	$ 206	$ 260