Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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.

+ References

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- Definition

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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-Publisher FASB
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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).

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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

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-Name Accounting Standards Codification
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- Definition

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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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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- Definition

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

+ 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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- Definition

Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

+ References

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-Section 50
-Paragraph 2
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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.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Stockbased Compensation, Restricted Units Disclosures (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Unvested Restricted Units [Roll Forward]
Unvested Restricted Units, Beginning Balance	1.4
Granted	0.6
Vested	(0.7)
Forfeited	(0.1)
Unvested Restricted Units, Ending Balance	1.2	1.4
Restricted Units, Additional Disclosures [Abstract]
Unvested Restricted Units, Weighted Average Grant Date Fair Value, Beginning Balance (in dollars per share)	$ 150.23
Granted, Weighted Average Grant Date Fair Value (in dollars per share)	204.72
Vested, Weighted Average Grant Date Fair Value (in dollars per share)	150.28
Forfeited, Weighted Average Grant Date Fair Value (in dollars per share)	166.95
Unvested Restricted Units, Weighted Average Grant Date Fair Value, Ending Balance (in dollars per share)	$ 177.04	$ 150.23
Fair Value of Units Vested	$ 114	$ 97	$ 91
Restricted Stock Units (RSUs) [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Requisite Service Period	3 years
Restricted Stock Units (RSUs) [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Requisite Service Period	4 years