Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, 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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

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

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.

+ References

No definition available.

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Stock-Based Compensation - Shares of Restricted Stock Granted under 2010 Plan (Details) - Plan 2010 - Restricted Stock - shares	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares	67,689
Remaining Term (In Years)	2 years 7 months 10 days
2014 \| Five Years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Term (In Years)				5 years
Shares	10,422
Remaining Term (In Years)				10 months 24 days
2015 \| Five Years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Term (In Years)			5 years
Shares	12,023
Remaining Term (In Years)			1 year 10 months 10 days
2016 \| Five Years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Term (In Years)			5 years
Shares	15,015
Remaining Term (In Years)			2 years 9 months 18 days
2017 \| Five Years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Term (In Years)		5 years
Shares	9,972
Remaining Term (In Years)		3 years 9 months 18 days
2017 \| Three Years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Term (In Years)		3 years
Shares	4,902
Remaining Term (In Years)		1 year 10 months 21 days
2018 \| Five Years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Term (In Years)	5 years
Shares	9,655
Remaining Term (In Years)	4 years 9 months 18 days
2018 \| Three Years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Term (In Years)	3 years
Shares	2,400
Remaining Term (In Years)	2 years 10 months 24 days
2018 \| One Year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Term (In Years)	1 year
Shares	300
Remaining Term (In Years)	10 months 24 days
2018 \| Two Years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Term (In Years)	2 years
Shares	932
Remaining Term (In Years)	1 year 9 months 18 days
2018 \| Four Years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Term (In Years)	4 years
Shares	2,068
Remaining Term (In Years)	3 years 9 months 18 days