Retirement-Related Benefits - Cost of Pension Plans (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | |||
|---|---|---|---|---|---|
Dec. 31, 2018 |
Sep. 30, 2019 |
Sep. 30, 2018 |
Sep. 30, 2019 |
Sep. 30, 2018 |
|
| Cost/(Income) of Pension Plans | |||||
| Total defined benefit and contribution pension plans cost recognized in the Consolidated Statement of Earnings | $ 459 | $ 705 | $ 1,337 | $ 2,152 | |
| U.S. | |||||
| Cost/(Income) of Pension Plans | |||||
| Total defined benefit and contribution pension plans cost recognized in the Consolidated Statement of Earnings | 115 | 292 | 333 | 876 | |
| U.S. | Pension Plans | |||||
| Cost/(Income) of Pension Plans | |||||
| Interest cost | $ 470 | $ 430 | $ 1,411 | $ 1,289 | |
| Interest cost - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | |
| Expected return on plan assets | $ (650) | $ (675) | $ (1,949) | $ (2,026) | |
| Expected return on plan assets - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | |
| Amortization of prior service costs/(credits) | $ 4 | $ 4 | $ 12 | $ 12 | |
| Amortization of prior service costs/(credits) - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | |
| Recognized actuarial losses | $ 140 | $ 381 | $ 419 | $ 1,144 | |
| 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 | |
| Other costs - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | |
| Total net periodic (income)/cost recognized for defined benefit plans | $ (36) | $ 140 | $ (107) | $ 419 | |
| Cost of defined contribution plans | 151 | 152 | 440 | 457 | |
| Average remaining life expectancy of inactive plan participants | 18 years | ||||
| Decrease in recognized actuarial losses due to substantially all plan participants considered inactive as of 2019 | 242 | 725 | |||
| Non-U.S. | |||||
| Cost/(Income) of Pension Plans | |||||
| Total defined benefit and contribution pension plans cost recognized in the Consolidated Statement of Earnings | 344 | 413 | 1,004 | 1,276 | |
| Non-U.S. | Pension Plans | |||||
| Cost/(Income) of Pension Plans | |||||
| Service cost | 93 | 104 | 279 | 309 | |
| Interest cost | $ 202 | $ 204 | $ 616 | $ 630 | |
| Interest cost - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | |
| Expected return on plan assets | $ (391) | $ (330) | $ (1,186) | $ (1,017) | |
| Expected return on plan assets - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | |
| Amortization of prior service costs/(credits) | $ (7) | $ (20) | $ (20) | $ (62) | |
| Amortization of prior service costs/(credits) - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | |
| Recognized actuarial losses | $ 313 | $ 346 | $ 939 | $ 1,057 | |
| Recognized actuarial losses - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | |
| Curtailments and settlements | $ 3 | $ 2 | $ 7 | $ 7 | |
| Curtailments and settlements - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | |
| Multi-employer plans | $ 10 | $ 9 | $ 26 | $ 29 | |
| Other costs | $ 11 | $ 5 | $ 22 | $ 16 | |
| Other costs - income statement location | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | ibm:OtherIncomeAndExpense | |
| Total net periodic (income)/cost recognized for defined benefit plans | $ 235 | $ 318 | $ 683 | $ 969 | |
| Cost of defined contribution plans | $ 109 | $ 95 | $ 321 | $ 306 | |