Borrowings - Long-Term Debt, Debt Issued (Details) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2021 |
Mar. 31, 2020 |
|
| Euro fixed-rate notes | ||
| Notes Issued | ||
| Aggregate amount of debt issued | $ 4,100 | |
| Fixed rate debt due in 2021 | ||
| Notes Issued | ||
| Outstanding debt redeemed | $ 2,900 | |
| Aggregate principal redeemed (as a percent) | 100.00% | |
| Loss upon redemption on notes | $ (49) | |
| IBM Credit LLC | Fixed rate debt due in 2021 to 2023 | ||
| Notes Issued | ||
| Outstanding debt redeemed | $ 1,750 | |
| Aggregate principal redeemed (as a percent) | 100.00% | |
| Loss upon redemption on notes | $ (22) | |