Software Development and Intellectual Property Licenses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Software development and intellectual property licenses:
Internally-developed software costs	$ 254		$ 254		$ 291
Payments made to third-party software developers	20		20		38
Total software development costs	274		274		$ 329
Amortization:
Amortization of capitalized software development costs and intellectual property licenses	$ 54	$ 57	$ 164	$ 209