Derivative Instruments - Derivatives in Accumulated Other Comprehensive Income (Details) - Foreign Exchange Contract - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2018 |
Sep. 30, 2017 |
Sep. 30, 2018 |
Sep. 30, 2017 |
|
| Effect of derivative Contracts on Accumulated Other Comprehensive Income | ||||
| Amount of Gain (Loss) Reclassified From AOCI to Earnings | $ 14 | $ (13) | $ (33) | $ 14 |
| Designated as Hedging Instrument | Cash Flow Hedging | ||||
| Effect of derivative Contracts on Accumulated Other Comprehensive Income | ||||
| Beginning balance | (57) | 54 | ||
| Amount of Gain (Loss) Recognized in Other Comprehensive Income | 54 | (94) | ||
| Amount of Gain (Loss) Reclassified From AOCI to Earnings | (37) | 28 | ||
| Ending balance | $ 34 | $ (68) | $ 34 | $ (68) |