Retirement-Related Benefits - Nonpension Postretirement Cost (Details) - Nonpension Postretirement Plans - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2019 |
Sep. 30, 2018 |
Sep. 30, 2019 |
Sep. 30, 2018 |
|
| U.S. | ||||
| Retirement-related plans cost | ||||
| Service cost | $ 3 | $ 3 | $ 8 | $ 10 |
| Interest cost | $ 36 | $ 33 | $ 109 | $ 99 |
| Interest cost - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense |
| Expected return on plan assets - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense |
| Amortization of prior service costs/(credits) | $ (1) | $ (2) | $ (2) | $ (6) |
| Amortization of prior service costs/(credits) - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense |
| Recognized actuarial losses | $ 0 | $ 2 | $ 0 | $ 7 |
| Recognized actuarial losses - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense |
| Curtailments and settlements - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense |
| Total net periodic (income)/cost recognized for defined benefit plans | $ 38 | $ 37 | $ 115 | $ 111 |
| Non-U.S. | ||||
| Retirement-related plans cost | ||||
| Service cost | 1 | 1 | 4 | 4 |
| Interest cost | $ 12 | $ 11 | $ 37 | $ 34 |
| Interest cost - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense |
| Expected return on plan assets | $ (1) | $ (1) | $ (4) | $ (4) |
| Expected return on plan assets - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense |
| Amortization of prior service costs/(credits) | $ 0 | $ 0 | $ 0 | $ 0 |
| Amortization of prior service costs/(credits) - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense |
| Recognized actuarial losses | $ 3 | $ 1 | $ 8 | $ 4 |
| Recognized actuarial losses - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense |
| Curtailments and settlements | $ 0 | $ 0 | $ 0 | |
| Curtailments and settlements - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense |
| Total net periodic (income)/cost recognized for defined benefit plans | $ 15 | $ 12 | $ 45 | $ 38 |