Unrecognized cost of unvested share-based compensation awards.

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.

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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.

+ 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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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

Number of additional shares authorized for issuance under an established share-based compensation plan.

+ References

No definition available.

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ 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 (d)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

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=96867065&loc=d3e5070-113901

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

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- Definition

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
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

Period from grant date that an equity-based award expires, 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)(2)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

Share Based Compensation Annual Increase In Number Of Shares

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No definition available.

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Share Based Compensation Arrangement By Share Based Payment Award Percentage Increase In Outstanding Shares

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Stock Compensation Plans - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended	12 Months Ended
	Jan. 03, 2018	Apr. 16, 2017	Oct. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Nov. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options expiration period				10 years
Options outstanding (in shares)				6,083,482	4,841,274
Weighted-average grant date fair value of stock options granted to employees and directors (usd per share)				$ 2.34	$ 5.70	$ 5.81
Non-Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost related to unvested stock option awards				$ 449
2014 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock for annual increase in shares available for issuance (in shares)				1,200,000
Percent of outstanding shares of common stock prior to each anniversary				3.00%
Number of additional shares authorized (in shares)		1,200,000
Aggregate number of shares outstanding or available for grant under the plan (in shares)				125,000
2014 Equity Incentive Plan \| Performance-Based Employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options expiration period				10 years
Options outstanding (in shares)				647,322
Option vesting under Equity Incentive Plans, term			3 years
Options exercise price, minimum (usd per share)				$ 4.57
Options exercise price, maximum (usd per share)				$ 7.69
Amended and Restated 2017 Inducement Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate number of shares outstanding or available for grant under the plan (in shares)							1,850,000
Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost related to unvested stock option awards				$ 6,200
Remaining weighted-average vesting period				1 year 8 months 12 days
Non-Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining weighted-average vesting period				2 years 1 month 6 days
Subsequent Event \| Non-Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost related to unvested stock option awards	$ 1,300
Subsequent Event \| Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost related to unvested stock option awards	$ 12,700
Remaining weighted-average vesting period	2 years 8 months 12 days
Subsequent Event \| Non-Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining weighted-average vesting period	2 years
Minimum \| 2014 Plan and 2012 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting under Equity Incentive Plans, term				1 year
Maximum \| 2014 Plan and 2012 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting under Equity Incentive Plans, term				4 years