Stock-based Compensation (Changes in Undistributed Performance Share Units) (Details) - $ / shares shares in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Weighted- Average Grant Date Fair Value per Share
Undistributed performance share units (in shares)	0.1
Weighted-average grant date fair value of undistributed performance share units (in usd per share)	$ 213.73
Undistributed and vested performance share units (in shares)	0.1
Performance Shares [Member]
Shares (2)
Undistributed as of beginning of period (in shares)	0.2
Distributed (in shares)	0.1
Undistributed as of end of period (in shares)	0.2	0.2
Weighted- Average Grant Date Fair Value per Share
Undistributed as of beginning of period (in usd per share)	$ 160.69
Granted (in usd per share)	245.06	$ 204.64	$ 197.54
Distributed (in usd per share)	126.31
Undistributed as of end of period (in usd per share)	$ 191.14	$ 160.69

Undistributed and unvested performance share units.

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Weighted average grant date fair value of undistributed performance.

+ References

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- Definition

Undistributed and Vested Performance Share Units

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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=116856206&loc=d3e5070-113901

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- Definition

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.

+ 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
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-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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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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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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- Definition

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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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-Paragraph 2
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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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