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Shareholders' Equity - Schedule of Stock Repurchases (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions | 3 Months Ended | 6 Months Ended | 111 Months Ended
--- | --- | --- | ---
Jun. 30, 2021 | Mar. 31, 2021 | Jun. 30, 2020 | Mar. 31, 2020 | Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2021
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |  |
Total repurchase cost | $ 242 | $ 50 |  | $ 463 |  |  |
2012 - Share Repurchase Program |  |  |  |  |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |  |
Shares purchased (in shares) | 1.1 |  | 0.0 |  | 1.3 | 2.2 | 138.5
Average price per share (in dollars per share) | $ 235.84 |  | $ 0 |  | $ 232.53 | $ 212.78 |
Total repurchase cost | $ 242 |  | $ 0 |  | $ 292 | $ 461 | $ 15,000
Additional associated costs | 0 |  | 0 |  | 0 | 2 |
Total costs recorded to retained earnings | $ 242 |  | $ 0 |  | $ 292 | $ 463 |

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