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Shareholders' equity Share Repurchases (Details) - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Apr. 29, 2021 | Mar. 31, 2021 | Mar. 31, 2020 | 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 |  |  | 2,266,150 |  |  |
Cost of shares repurchased |  |  | $ 326 |  |  |
Repurchase authorization remaining at end of period |  |  | $ 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 |  | 3,110,000 |  |  |  |
Cost of shares repurchased |  | $ 519 |  |  |  |
Repurchase authorization remaining at end of period |  | $ 1,982 |  |  |  |
CB_Increase(Decrease)StockRepurchaseProgramAuthorizedAmount |  |  |  | $ 1,000 |  |
Subsequent Event [Member] | Nov 2020 Stock Repurchase Plan |  |  |  |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |
Number of shares repurchased | 450,000 |  |  |  |  |
Cost of shares repurchased | $ 76 |  |  |  |  |
Repurchase authorization remaining at end of period | $ 1,906 |  |  |  |  |

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