Reconciliation of Numerator and Denominator for Basic and Diluted Earnings Per Share (Details) - USD ($) shares in Millions, $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2016 |
Sep. 30, 2015 |
Sep. 30, 2016 |
Sep. 30, 2015 |
|
| Earnings Per Share [Abstract] | ||||
| Net income attributable to common stockholders | $ 148 | $ 174 | $ 367 | $ 377 |
| Weighted-average common shares outstanding—Basic | 178 | 179 | 178 | 179 |
| Effect of dilutive common stock equivalents | 1 | 1 | 1 | |
| Weighted-average common shares outstanding—Diluted | 178 | 180 | 179 | 180 |