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Equity - Narrative (Details) - USD ($) $ in Millions |  | 12 Months Ended |
--- | --- | --- | ---
Oct. 29, 2018 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Oct. 25, 2018
Equity [Abstract] |  |  |  |  |
Common stock, shares authorized |  | 6,500,000,000 | 6,500,000,000 |  |
Preferred stock, shares authorized |  | 20,000,000 |  |  |
Accelerated Share Repurchases [Line Items] |  |  |  |  |
Treasury stock acquired |  | $ 9,091 | $ 4,014 | $ 3,434 |
Accelerated Share Repurchase Agreement, October 29, 2018 |  |  |  |  |
Accelerated Share Repurchases [Line Items] |  |  |  |  |
Purchases of treasury stock (in shares) | 56,700,000 |  |  |  |
Accelerated Share Repurchase Agreement |  |  |  |  |
Accelerated Share Repurchases [Line Items] |  |  |  |  |
Shares authorized to be repurchased (in shares) |  |  |  |  | $ 5,000
Payment under ASR agreement | $ 5,000 |  |  |  |
Treasury stock acquired | 4,000 |  |  |  |
Decrease in other-paid-in capital | $ 1,000 |  |  |  |

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