Derivative instruments (Effective Portion of Unrealized Gain (Loss)) (Details) - Cash flow hedge [Member] - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2021 |
Sep. 30, 2020 |
Sep. 30, 2021 |
Sep. 30, 2020 |
|
| Derivative Instruments, Gain (Loss) [Line Items] | ||||
| Total unrealized gains (losses) | $ 16 | $ 60 | $ 93 | $ (132) |
| Foreign currency contracts [Member] | ||||
| Derivative Instruments, Gain (Loss) [Line Items] | ||||
| Total unrealized gains (losses) | 136 | (163) | 273 | (25) |
| Cross-currency swap contracts [Member] | ||||
| Derivative Instruments, Gain (Loss) [Line Items] | ||||
| Total unrealized gains (losses) | $ (120) | $ 223 | $ (180) | $ (107) |