Equity-Based Compensation - Summary of Activity Related to Stock Options (Details) - Stock Options - $ / shares	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number Outstanding
Beginning Balance	2,436,232	2,822,728	3,081,203
Exercises	(351,904)	(279,277)
Forfeitures or expirations	(67,261)	(107,219)	(258,475)
Ending Balance	2,017,067	2,436,232	2,822,728
Weighted-Average Exercise Price Per Share
Beginning Balance	$ 17.95	$ 17.95	$ 17.95
Exercises	17.95	17.95	17.95
Forfeitures or expirations	17.95	17.95	17.95
Ending Balance	$ 17.95	$ 17.95	$ 17.95

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.

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Weighted average price of options that were either forfeited or expired.

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Number of options outstanding, including both vested and non-vested options.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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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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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Number of share options (or share units) exercised during the current period.

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