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Stock-based Compensation (Schedule of Stock Option Activities) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2021 | Dec. 31, 2020
Stock Options [Member] |  |
Stock Option Activity [Abstract] |  |
Stock options, shares outstanding at January 1, 2021 | 2,569 |
Stock options, shares granted | 387 |
Stock options, shares exercised | (356) |
Stock options, shares forfeited or expired | (90) |
Stock options, shares outstanding at September 30, 2021 | 2,510 | 2,569
Stock options, shares vested or expected to vest at September 30, 2021 | 2,486 |
Stock options, shares exercisable at September 30, 2021 | 1,731 |
Stock options weighted-average exercise price, outstanding at January 1, 2021 | $ 132.49 |
Stock options weighted-average exercise price, granted | 204.45 |
Stock options weighted-average exercise price, exercised | 121.82 |
Stock options weighted-average exercise price, forfeited or expired | 159.45 |
Stock options weighted-average exercise price, outstanding at September 30, 2021 | 144.13 | $ 132.49
Stock options weighted-average exercise price, vested or expected to vest at September 30, 2021 | 143.82 |
Stock options weighted-average exercise price, options exercisable at September 30, 2021 | $ 123.54 |
Stock options weighted-average remaining contractual term in years, outstanding at January 1, 2021 | 6 years 2 months 12 days | 6 years 4 months 24 days
Stock options weighted-average remaining contractual term in years, outstanding at September 30, 2021 | 6 years 2 months 12 days | 6 years 4 months 24 days
Stock options weighted-average remaining contractual term in years, vested or expected to vest at September 30, 2021 | 6 years 2 months 12 days |
Stock options weighted-average remaining contractual term in years, options exercisable at September 30, 2021 | 5 years 1 month 6 days |
Stock options aggregate intrinsic value, outstanding at January 1, 2021 | $ 195 |
Stock options aggregate intrinsic value, outstanding at September 30, 2021 | 133 | $ 195
Stock options aggregate intrinsic value, vested or expected to vest at September 30, 2021 | 133 |
Stock options aggregate intrinsic value, options exercisable at September 30, 2021 | $ 125 |
Retention Awards [Member] |  |
Awards Activity [Abstract] |  |
Awards, shares nonvested at January 1, 2021 | 1,476 |
Awards, shares granted | 289 |
Awards, shares vested | (414) |
Awards, shares forfeited | (53) |
Awards, shares nonvested at September 30, 2021 | 1,298 | 1,476
Awards weighted-average grant-date fair value, nonvested at January 1, 2021 | $ 141.06 |
Awards weighted-average grant-date fair value, granted | 205.10 |
Awards weighted-average grant-date fair value, vested | 108.32 |
Awards weighted-average grant-date fair value, forfeited | 162.23 |
Awards weighted-average grant-date fair value, nonvested at September 30, 2021 | $ 164.90 | $ 141.06
Performance Retention Awards [Member] |  |
Awards Activity [Abstract] |  |
Awards, shares nonvested at January 1, 2021 | 773 |
Awards, shares granted | 227 |
Awards, shares vested | (147) |
Awards, shares unearned | (165) |
Awards, shares forfeited | (41) |
Awards, shares nonvested at September 30, 2021 | 647 | 773
Awards weighted-average grant-date fair value, nonvested at January 1, 2021 | $ 148.17 |
Awards weighted-average grant-date fair value, granted | 204.45 |
Awards weighted-average grant-date fair value, vested | 132.66 |
Awards weighted-average grant-date fair value, unearned | 135.57 |
Awards weighted-average grant-date fair value, forfeited | 183.55 |
Awards weighted-average grant-date fair value, nonvested at September 30, 2021 | $ 172.41 | $ 148.17

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- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + 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 (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options. + 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 (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the 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 2 -Subparagraph (c)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan. + 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 (c)(1)(iii) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired. + 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 (c)(1)(iv)(3)-(4) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Weighted average price of options that were either forfeited or expired. + 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 (c)(1)(iv)(3)-(4) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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