Period between the occurrence of a specified event and the expiration of the outstanding option.

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- Definition

Total amount of additional stock-based compensation cost recognized from occurrence of event accelerating recognition of cost and the excess of fair value of modified award over the fair value of the award immediately before modification.

+ References

No definition available.

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- Definition

Share Based Compensation Arrangement By Share Based Payment Award Options Vested Grant Date Fair Value

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No definition available.

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- Definition

Aggregate number of common shares reserved for future issuance.

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- Definition

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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- Definition

Amount of cost to be recognized for option under share-based payment arrangement.

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- Definition

Description of terms of share-based payment arrangement. Includes, but is not limited to, type of award or grantee and reason for issuance.

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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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- Definition

Number of additional shares authorized for issuance under share-based payment arrangement.

+ References

No definition available.

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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.

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- Definition

Maximum number of shares that may be issued in accordance with the plan as a proportion of outstanding capital stock.

+ References

No definition available.

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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.

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Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	3 Months Ended		6 Months Ended
	Jan. 21, 2020	May 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock shares reserved for issuance			16,386,314		16,386,314		18,577,117
2015 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock shares reserved for issuance			4,678,379		4,678,379
Stock option life in years					10 years
Stock option grants description					The number of shares reserved for issuance under the 2015 Plan will increase automatically on January 1 of each calendar year 2016 through 2025 by the number of shares equal to 4% of the total outstanding shares of the Company’s common stock as of the immediately preceding December 31.
Percentage threshold of outstanding shares increased annually under the plan					4.00%
Common shares authorized to be issued during the period	4,312,500
2015 Plan [Member] \| Contract Termination [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrant expiration period after specified event		75 days
2008 Plan, 2015 Plan and 2018 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair values of options granted			$ 10.14	$ 20.80	$ 8.69	$ 56.00
Total grant date fair value of options vested			$ 2.2	$ 1.7	$ 3.8	$ 4.3
Total unrecognized stock-based compensation related to unvested stock options			$ 19.2		$ 19.2
Weighted-average period					3 years 3 months 18 days
Common shares authorized to be issued during the period					4,887,187
2018 Equity Inducement Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock shares reserved for issuance			537,500		537,500			37,500
Common shares authorized to be issued during the period					500,000
2018 Plan [Member] \| Contract Termination [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation costs relating to vesting acceleration and modification			$ 2.2		$ 2.2