Stock Based Compensation - Stock Based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock based compensation expense	$ 11	$ 11	$ 20	$ 20
Cost of providing services
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock based compensation expense	3	2	5	4
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock based compensation expense	1	1	3	1
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock based compensation expense	6	7	11	13
Systems development and programming costs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock based compensation expense	$ 1	$ 1	$ 1	$ 2