Stockholders' Equity - Stock-Based Compensation Expense (Details) - USD ($)
$ in Millions |
3 Months Ended |
Mar. 31, 2018 |
Mar. 31, 2017 |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
| Stock-based compensation expense |
$ 9
|
$ 6
|
| Income tax benefit related to stock-based compensation expense |
2
|
2
|
| Tax benefit realized from stock options exercised and similar awards |
6
|
6
|
| Cost of providing services |
|
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
| Stock-based compensation expense |
2
|
2
|
| Sales and marketing |
|
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
| Stock-based compensation expense |
2
|
1
|
| General and administrative |
|
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
| Stock-based compensation expense |
4
|
2
|
| Systems development and programming costs |
|
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
| Stock-based compensation expense |
$ 1
|
$ 1
|