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Stock Plans and Share-Based Compensation - Share-Based Compensation and Related Income Tax Benefit (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Total Share-based Compensation Expense | $ 29 | $ 74 | $ 51
Income Tax Benefit | 19 | 43 | 26
Stock Options |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Total Share-based Compensation Expense | 19 | 18 | 13
Restricted Stock Units and Awards |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Total Share-based Compensation Expense | 6 | 8 | 6
Employee Stock Purchase Plan |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Total Share-based Compensation Expense | 5 | 4 | 2
Stock Awards for Directors |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Total Share-based Compensation Expense | 2 | 2 | 2
Performance Units |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Total Share-based Compensation Expense | $ (3) | $ 42 | $ 28

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