Stock-based Compensation (Changes in Undistributed Performance Share Units) (Details) - $ / shares	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Weighted- Average Grant Date Fair Value per Share
Undistributed performance share units (in shares)	114,500
Weighted-average grant date fair value of undistributed performance share units (in usd per share)	$ 235.71
Undistributed and vested performance share units (in shares)	44,900
Performance Shares [Member]
Shares
Undistributed as of beginning of period (in shares)	202,300,000
Granted (in shares)	33,600,000
Distributed (in shares)	72,000,000.0
Forfeited (in shares)	(4,500,000)
Undistributed as of end of period (in shares)	159,400,000	202,300,000
Weighted- Average Grant Date Fair Value per Share
Undistributed as of beginning of period (in usd per share)	$ 191.14
Granted (in usd per share)	265.96	$ 245.06	$ 204.64
Distributed (in usd per share)	150.21
Forfeited (in usd per share)	205.99
Undistributed as of end of period (in usd per share)	$ 224.95	$ 191.14

Undistributed and unvested performance share units.

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Weighted average grant date fair value of undistributed performance.

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Undistributed and Vested Performance Share Units

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made 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).

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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).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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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.

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