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Stock-based Compensation (Schedule of Stock Option Exercises) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019
Stock Option Aggregate Disclosures [Abstract] |  |  |  |
Intrinsic value of stock options exercised | $ 40 | $ 10 | $ 105 | $ 174
Cash received from option exercises | 29 | 10 | 80 | 108
Treasury shares repurchased for employee payroll taxes | (8) | (3) | (20) | (32)
Tax benefit realized from option exercises | 11 | 3 | 25 | 43
Aggregate grant-date fair value of stock options vested |  |  | $ 14 | $ 15

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