Equity-Based Compensation - Summary of Restricted Stock Activity Under the 2010 Plan, Equity Plan and the 1991 Restricted Stock Plan (Details) - Restricted Stock [Member] - $ / shares	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
2010 Equity Award Plan [Member]
Restricted Stock Activity
Beginning of period, outstanding (in shares)	507,036	406,918	77,624
Restricted stock grants (in shares)	483,800	292,342	537,160
Released (in shares)	(104,516)	(101,960)	(19,130)
Canceled or forfeited (in shares)	(35,393)	(90,264)	(188,736)
End of period, outstanding (in shares)	850,927	507,036	406,918
Weighted-Average Fair Value
Beginning of period (weighted-average fair value)	$ 5.40	$ 5.14	$ 8.44
Restricted stock grants (weighted-average fair value)	7.61	5.66	4.74
Released (weighted-average fair value)	5.52	5.39	8.82
Canceled or forfeited (weighted-average fair value)	5.11	5.11	4.97
End of period (weighted-average fair value)	$ 6.65	$ 5.40	$ 5.14
2000 Equity Award Plan [Member]
Restricted Stock Activity
Beginning of period, outstanding (in shares)	40,000	61,500	141,500
Released (in shares)		(21,500)	(80,000)
End of period, outstanding (in shares)	40,000	40,000	61,500
Weighted-Average Fair Value
Beginning of period (weighted-average fair value)	$ 4.97	$ 5.13	$ 5.04
Released (weighted-average fair value)		5.44	4.97
End of period (weighted-average fair value)	$ 4.97	$ 4.97	$ 5.13
1991 Equity Award Plan [Member]
Restricted Stock Activity
Beginning of period, outstanding (in shares)	90,454	84,352	189,525
Restricted stock grants (in shares)		57,900	16,371
Released (in shares)	(31,937)	(32,823)	(66,269)
Canceled or forfeited (in shares)	(2,400)	(18,975)	(55,275)
End of period, outstanding (in shares)	56,117	90,454	84,352
Weighted-Average Fair Value
Beginning of period (weighted-average fair value)	$ 6.76	$ 10.96	$ 11.48
Restricted stock grants (weighted-average fair value)		5.75	4.95
Released (weighted-average fair value)	8.41	14.41	13.05
Canceled or forfeited (weighted-average fair value)	5.75	9.10	8.45
End of period (weighted-average fair value)	$ 5.87	$ 6.76	$ 10.96

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

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)(1)(iv)(3)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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

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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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