Stock-Based Compensation - Stock Option Activity (Detail) shares in Thousands	3 Months Ended
Mar. 31, 2019 $ / shares shares
Options
Outstanding as of beginning of period \| shares	5,020
Granted \| shares	2,343
Exercised \| shares	0
Forfeited \| shares	(16)
Outstanding as of end of period \| shares	7,347
Weighted- Average Exercise Price
Outstanding as of beginning of period \| $ / shares	$ 5.62
Granted \| $ / shares	2.02
Exercised \| $ / shares	0
Forfeited \| $ / shares	3.70
Outstanding as of end of period \| $ / shares	$ 4.48

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.

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- Definition

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

+ References

No definition available.

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 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.

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- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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- Definition

Weighted average price at which option holders acquired shares when converting their stock options into shares.

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- Definition

Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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- Definition

Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

+ References

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- Definition

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

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