Basis of Presentation and Significant Accounting Policies - Accrued Rebates and Other Accruals (Details) - USD ($) $ in Millions |
Dec. 31, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Schedule Of Accrued Liabilities [Line Items] | ||
| Accrued rebates and other accruals | $ 5,689 | $ 5,426 |
| Trade accounts receivable, less allowance for doubtful accounts [Member] | ||
| Schedule Of Accrued Liabilities [Line Items] | ||
| Accrued rebates and other accruals | 1,257 | 1,288 |
| Other current liabilities [Member] | ||
| Schedule Of Accrued Liabilities [Line Items] | ||
| Accrued rebates | 3,285 | 3,208 |
| Other accruals | 581 | 531 |
| Other noncurrent liabilities [Member] | ||
| Schedule Of Accrued Liabilities [Line Items] | ||
| Accrued rebates and other accruals | $ 565 | $ 399 |