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Shareholders' Equity - Schedule of Stock Repurchases (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions | 3 Months Ended | 9 Months Ended | 114 Months Ended
--- | --- | --- | ---
Sep. 30, 2021 | Jun. 30, 2021 | Mar. 31, 2021 | Sep. 30, 2020 | Mar. 31, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |  |  |
Total repurchase cost | $ 1,251 | $ 242 | $ 50 | $ 500 | $ 463 |  |  |
2012 - Share Repurchase Program |  |  |  |  |  |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |  |  |
Shares purchased (in shares) | 4.4 |  |  | 2.4 |  | 5.7 | 4.6 | 142.9
Average price per share (in dollars per share) | $ 283.38 |  |  | $ 201.96 |  | $ 272.11 | $ 207.01 |
Total repurchase cost | $ 1,251 |  |  | $ 500 |  | $ 1,543 | $ 961 | $ 16,300
Additional associated costs | 0 |  |  | 0 |  | 0 | 2 |
Total costs recorded to retained earnings | $ 1,251 |  |  | $ 500 |  | $ 1,543 | $ 963 |

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