The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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)(iii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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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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The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Equity-Based Compensation (Summary of the range of exercise prices and the weighted average remaining contractual life of the options) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Line Items
Number of Options Outstanding	845,619	917,269	951,523	888,571
Weighted Average Exercise Price outstanding	$ 14.14	$ 14.08	$ 12.45	$ 14.12
Weighted Average Contract Life Remaining	4 years 8 months
Number of Options Exercisable	611,149
Weighted Average Exercise Price	$ 13.2
Price Range One [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Line Items
Range of Exercise Prices - Lower Range	5.63
Range of Exercise Prices -Upper Range	$ 8.45
Number of Options Outstanding	4,078
Weighted Average Exercise Price outstanding	$ 8.28
Weighted Average Contract Life Remaining	1 year 4 months
Number of Options Exercisable	4,078
Weighted Average Exercise Price	$ 8.28
Price Range Two [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Line Items
Range of Exercise Prices - Lower Range	8.46
Range of Exercise Prices -Upper Range	$ 11.26
Number of Options Outstanding	0
Weighted Average Exercise Price outstanding	$ 0
Weighted Average Contract Life Remaining	0 years
Number of Options Exercisable	0
Weighted Average Exercise Price	$ 0
Price Range Three [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Line Items
Range of Exercise Prices - Lower Range	11.27
Range of Exercise Prices -Upper Range	$ 14.08
Number of Options Outstanding	388,241
Weighted Average Exercise Price outstanding	$ 11.85
Weighted Average Contract Life Remaining	3 years
Number of Options Exercisable	388,241
Weighted Average Exercise Price	$ 11.85
Price Range Four [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Line Items
Range of Exercise Prices - Lower Range	14.09
Range of Exercise Prices -Upper Range	$ 16.9
Number of Options Outstanding	286,575
Weighted Average Exercise Price outstanding	$ 15.38
Weighted Average Contract Life Remaining	5 years 8 months
Number of Options Exercisable	176,025
Weighted Average Exercise Price	$ 15.22
Price Range Five [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Line Items
Range of Exercise Prices - Lower Range	16.91
Range of Exercise Prices -Upper Range	$ 19.71
Number of Options Outstanding	165,225
Weighted Average Exercise Price outstanding	$ 17.44
Weighted Average Contract Life Remaining	7 years 2 months
Number of Options Exercisable	41,305
Weighted Average Exercise Price	$ 17.44
Price Range Six [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Line Items
Range of Exercise Prices - Lower Range	19.72
Range of Exercise Prices -Upper Range	$ 22.53
Number of Options Outstanding	1,500
Weighted Average Exercise Price outstanding	$ 21.86
Weighted Average Contract Life Remaining	2 months
Number of Options Exercisable	1,500
Weighted Average Exercise Price	$ 21.86