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Stock-based Compensation (Schedule of Stock Option Exercises) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Stock Option Aggregate Disclosures [Abstract] |  |  |  |
Intrinsic value of stock options exercised | $ 1 | $ 40 | $ 33 | $ 105
Cash received from option exercises | 1 | 29 | 35 | 80
Treasury shares repurchased for employee payroll taxes |  | (8) | (7) | (20)
Tax benefit realized from option exercises |  | 11 | 6 | 25
Aggregate grant-date fair value of stock options vested |  |  | $ 14 | $ 14

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- Definition Amount of tax benefit from exercise of option under share-based payment arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=120381028&loc=SL79508275-113901 + Details
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- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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