Aggregate number of common shares reserved for future issuance.

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Unrecognized cost of unvested share-based compensation awards.

+ 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 (i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

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.

+ References

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Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

+ References

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- Definition

Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
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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.

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

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No definition available.

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- Definition

Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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

Net number of share options (or share units) granted during the period.

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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-Paragraph 2
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Number of options outstanding, including both vested and non-vested options.

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-Publisher FASB
-Name Accounting Standards Codification
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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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No definition available.

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- Definition

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.

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

Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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Share based compensation arrangement by share based payment award contractual life.

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No definition available.

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Share based compensation arrangement by share based payment award options grants grant date fair value.

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No definition available.

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Stock Repurchased During Period Per Share

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Stock Option Plan - Additional information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended											12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	May 31, 2017	Dec. 31, 2016	Jun. 30, 2016	May 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	May 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2012	Dec. 31, 2014	Jun. 18, 2014	May 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance	526,364											526,364
Outstanding options issued	3,852,135				3,465,335			3,481,468				3,852,135	3,465,335	3,481,468		6,505,663
Proceeds from stock options exercised												$ 88	$ 714	$ 4,568
Total intrinsic value of options												$ 300	$ 1,500	$ 23,800
Stock options, granted												688,800	362,800	427,800
Stock options granted exercise price												$ 5.27	$ 6.40	$ 10.47
Stock options contractual life												6 years 5 months 20 days
Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period															3 years
Contractual terms															10 years
Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual terms															10 years
Director \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period															3 years
Director \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period															1 year
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Repurchase of shares of restricted common stock	245,602		16,666	132,000	119,873	6,667	116,667	16,709	7,669
Repurchase of shares of restricted common stock, price per share	$ 4.14		$ 6.11	$ 7.12	$ 5.35	$ 7.74	$ 6.86	$ 8.31	$ 11.57
Restricted Stock \| Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years				3 years			3 years		3 years	3 years
Share-based payment award granted	838,000				625,750			403,083		50,000	1,000,000
Restricted Stock \| Non Employee Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year				1 year			1 year
Share-based payment award granted	69,032				86,020			133,305	4,186
Unvested Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs related to non-vested restricted stock outstanding	$ 5,100											$ 5,100
Expected recognition period												1 year 8 months 23 days
Unvested Restricted Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected recognition period												1 year 7 months 2 days
Share-based payment award granted												907,032	711,770	1,590,574
Unrecognized stock-based compensation expense related to non-vested restricted stock arrangements	$ 8,200											$ 8,200
the "2012 Plan"
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance	9,000,000											9,000,000					5,000,000	4,000,000
the "2012 Plan" \| Employees \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding options issued	3,214,635											3,214,635
the "2012 Plan" \| Director \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding options issued	627,500											627,500
the "2012 Plan" \| Consultants \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding options issued	10,000											10,000
Outside 2012 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding options issued	500,000											500,000
Vesting period		3 years
Stock options, granted		500,000
Stock options granted exercise price		$ 6.16
Stock options contractual life		10 years
Share Based compensation arrangement by share based payment award options grants grant date fair value		$ 2,200