Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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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.

+ References

No definition available.

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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://fasb.org/us-gaap/role/ref/legacyRef
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- Definition

The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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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.

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- Definition

The weighted average price as of the balance sheet date at which grantees could acquire the underlying shares with respect to all outstanding stock options which are in the customized range of exercise prices.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Paragraph 2
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- Definition

Weighted average remaining contractual term of outstanding stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Stockholders' Equity - Summary of Stock Options Outstanding (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number Outstanding	4,406,004
Aggregate Intrinsic Value	$ 4,172	$ 1,190	$ 0	$ 3,124
$1.00 - 5.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 1.00
Range of Exercise Prices, maximum	$ 5
Number Outstanding	3,948,887
Weighted Average Remaining Contractual Life (Years)	7 years 8 months 19 days
Weighted Average Exercise Price	$ 2.70
$5.01 - 10.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	5.01
Range of Exercise Prices, maximum	$ 10
Number Outstanding	387,361
Weighted Average Remaining Contractual Life (Years)	4 years 9 months 10 days
Weighted Average Exercise Price	$ 5.91
$ 10.01 - 15.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	10.01
Range of Exercise Prices, maximum	$ 15
Number Outstanding	38,756
Weighted Average Remaining Contractual Life (Years)	6 years 1 month 24 days
Weighted Average Exercise Price	$ 13.09
$15.01 - 20.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	15.01
Range of Exercise Prices, maximum	$ 20
Number Outstanding	31,000
Weighted Average Remaining Contractual Life (Years)	6 years
Weighted Average Exercise Price	$ 16.20