Basis of Presentation and Significant Accounting Policies - Impact of Lease Standard Adoption (Details) - USD ($) $ in Millions |
Dec. 31, 2019 |
Jan. 01, 2019 |
Dec. 31, 2018 |
|---|---|---|---|
| New Accounting Pronouncements or Change in Accounting Principle [Line Items] | |||
| Other current assets | $ 2,600 | $ 2,460 | $ 2,461 |
| Noncurrent deferred tax assets and other noncurrent tax assets | 2,099 | 1,913 | 1,924 |
| Other noncurrent assets | 4,450 | 4,149 | 2,799 |
| Other current liabilities | 11,083 | 11,011 | 10,753 |
| Other noncurrent liabilities | 6,317 | 6,910 | 5,850 |
| Retained earnings | $ 97,670 | 89,574 | $ 89,554 |
| Accounting Standards Update 2016-02 [Member] | |||
| New Accounting Pronouncements or Change in Accounting Principle [Line Items] | |||
| Other current assets | (1) | ||
| Noncurrent deferred tax assets and other noncurrent tax assets | (11) | ||
| Other noncurrent assets | 1,351 | ||
| Other current liabilities | 258 | ||
| Other noncurrent liabilities | 1,060 | ||
| Retained earnings | $ 20 |