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Share-based Compensation Plans - Share-based compensation expense recognized in continuing operations (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Total share-based compensation expense | $ 317 | $ 338 | $ 319
Tax benefit | 66 | 74 | 73
Share-based compensation expense, net of tax | 251 | 264 | 246
Employee share purchase plans |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Total share-based compensation expense | 9 | 9 | 10
Restricted share units (“RSUs”) |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Total share-based compensation expense | 198 | 186 | 182
Performance share awards (“PSAs”) |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Total share-based compensation expense | $ 110 | $ 143 | $ 127

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