Segment Information - Total Revenue by Geographic Region (Detail) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2019 |
Jun. 30, 2018 |
Jun. 30, 2019 |
Jun. 30, 2018 |
|
| Segment Reporting Information [Line Items] | ||||
| Revenue | $ 3,524 | $ 3,605 | $ 6,870 | $ 7,188 |
| Americas [Member] | ||||
| Segment Reporting Information [Line Items] | ||||
| Revenue | 2,366 | 2,337 | 4,606 | 4,661 |
| Europe [Member] | ||||
| Segment Reporting Information [Line Items] | ||||
| Revenue | 995 | 1,082 | 1,938 | 2,175 |
| Asia-Pacific [Member] | ||||
| Segment Reporting Information [Line Items] | ||||
| Revenue | $ 163 | $ 186 | $ 326 | $ 352 |