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Stock-Based Compensation - Schedule of PSU Activity (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Related tax benefit realized | $ 1 | $ 8 | $ 13 | $ 24
PSUs |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
PSUs vested (in shares) |  |  | 78,727 | 235,935
Common Stock issued net of tax withholding (in shares) |  |  | 49,967 | 156,450
Related tax benefit realized |  |  | $ 1 | $ 7

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