Stock Based Compensation - Stock Based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock based compensation expense	$ 11	$ 9
Cost of providing services
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock based compensation expense	3	2
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock based compensation expense	1	2
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock based compensation expense	6	5
Systems development and programming costs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock based compensation expense	$ 1	$ 0