Stockholder's Equity and Stock-Based Compensation Expense - Activity Related to Stock Options, Restricted Stock Restricted Stock Unit Awards and Stock Appreciation Rights (Details)	9 Months Ended
Sep. 30, 2018 shares
Stock Options and Stock Appreciation Rights
Ending balance (In shares)	804,936
Stock Options
Stock Options and Stock Appreciation Rights
Beginning balance (in shares)	890,341
Granted (in shares)	10,000
Exercised (in shares)	(70,086)
Cancelled/forfeited (in shares)	(25,319)
Ending balance (In shares)	804,936
Restricted Stock and Unit Awards
Restricted Stock and Unit Awards
Beginning balance (in shares)	201,702
Granted (in shares)	66,773
Vested (in shares)	(137,844)
Cancelled/forfeited (in shares)	(2,500)
Ending balance (in shares)	128,131
Stock Appreciation Rights
Stock Options and Stock Appreciation Rights
Beginning balance (in shares)	565,864
Granted (in shares)	0
Exercised (in shares)	(34,999)
Cancelled/forfeited (in shares)	0
Ending balance (In shares)	530,865

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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=96867065&loc=d3e5070-113901

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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=96867065&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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(2)
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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.

+ References

No definition available.

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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.

+ References

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-Publisher FASB
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-SubTopic 10
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-Paragraph 2
-Subparagraph (c)(1)(iv)(3)-(4)
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Gross number of share options (or share units) granted during the period.

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No definition available.

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- Definition

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

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+ References

No definition available.

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
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