Stock Based Compensation - Stock Based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Additional Disclosures for equity-based plans
Total stock based compensation expense	$ 41	$ 44	$ 32
Total stock based compensation capitalized	1	0	0
Income tax benefit related to stock based compensation expense	11	11	7
Tax benefit realized from stock options exercised and similar awards	18	23	28
Cost of providing services
Additional Disclosures for equity-based plans
Total stock based compensation expense	8	10	8
Sales and marketing
Additional Disclosures for equity-based plans
Total stock based compensation expense	3	8	6
General and administrative
Additional Disclosures for equity-based plans
Total stock based compensation expense	28	22	14
Systems development and programming costs
Additional Disclosures for equity-based plans
Total stock based compensation expense	$ 2	$ 4	$ 4