Equity-Based Compensation - Restricted Stock Unit Activity (Details) - Restricted Stock Units (RSUs) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of Units (in shares):
Nonvested beginning of period (in shares)	260,173
Grants (in shares)	58,577
Vested (in shares)	(88,097)
Forfeited (in shares)	(21,275)
Nonvested end of period (in shares)	209,378	260,173
Equity Instruments Other Than Options, Weighted Average Grant Date Fair Value (in dollars per share):
Beginning nonvested, weighted average grant date fair value (in dollars per share)	$ 59.56
Granted, weighted average grant date fair value (in dollars per share)	103.24	$ 73.95	$ 58.90
Vested, weighted average grant date fair value (in dollars per share	44.62
Forfeited, weighted average grant date fair value (in dollars per share	78.52
Ending nonvested, weighted average grant date fair value (in dollars per share)	$ 75.56	$ 59.56
Vested in period, fair value (less than)	$ 4	$ 2	$ 18

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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
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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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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.

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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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