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Shareholders' equity Share Repurchases (Details) - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended | 9 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Oct. 27, 2021 | Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Jul. 19, 2021 | Feb. 01, 2021 | Nov. 19, 2020 | Nov. 21, 2019
Nov 2019 Stock Repurchase Plan [Member] |  |  |  |  |  |  |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |  |  |  |
Stock Repurchase Program, Authorized Amount |  |  |  |  |  |  |  |  | $ 1,500
Number of shares repurchased |  |  | 0 |  | 2,266,150 |  |  |  |
Cost of shares repurchased |  |  | $ 0 |  | $ 326 |  |  |  |
Repurchase authorization remaining at end of period |  |  | $ 1,124 |  | $ 1,124 |  |  |  |
Nov 2020 Stock Repurchase Plan |  |  |  |  |  |  |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |  |  |  |
Stock Repurchase Program, Authorized Amount |  |  |  |  |  |  | $ 2,500 | $ 1,500 |
Number of shares repurchased |  |  |  | 22,877,400 |  |  |  |  |
Cost of shares repurchased |  |  |  | $ 3,956 |  |  |  |  |
CB_Increase(Decrease)StockRepurchaseProgramAuthorizedAmount |  |  |  |  |  |  | $ 1,000 |  |
July 2021 Stock Repurchase Plan |  |  |  |  |  |  |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |  |  |  |
Stock Repurchase Program, Authorized Amount |  |  |  |  |  | $ 5,000 |  |  |
Number of shares repurchased |  | 8,412,000 |  |  |  |  |  |  |
Cost of shares repurchased |  | $ 1,516 |  |  |  |  |  |  |
Repurchase authorization remaining at end of period |  | $ 3,551 |  | $ 3,551 |  |  |  |  |
Subsequent Event [Member] | July 2021 Stock Repurchase Plan |  |  |  |  |  |  |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |  |  |  |
Number of shares repurchased | 167,700 |  |  |  |  |  |  |  |
Cost of shares repurchased | $ 29 |  |  |  |  |  |  |  |
Repurchase authorization remaining at end of period | $ 3,522 |  |  |  |  |  |  |  |

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