Stockholders' Equity - Company's Stock Option Activity (Detail) (USD $)	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
2003 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding Options, Beginning balance	857,391
Outstanding Options, exercised	(67,295)
Outstanding Options, forfeited	0
Outstanding Options, Ending balance	790,096	857,391
Vested or expected to vest outstanding options	789,113
Exercisable outstanding options	757,897
Weighted-Average Exercise Price, Outstanding Beginning balance	$ 1.26
Weighted-Average Exercise Price, Options exercised	$ 1.12
Weighted-Average Exercise Price, Options forfeited	$ 0
Weighted-Average Exercise Price, Outstanding Ending balance	$ 1.27	$ 1.26
Weighted-Average Exercise Price, Vested or expected to vest	$ 1.27
Weighted-Average Exercise Price, Exercisable	$ 1.23
Weighted-Average Remaining Contractual Term, Outstanding	4 years 11 months 23 days	5 years 2 months 12 days
Weighted-Average Remaining Contractual Term, Vested or expected to vest	4 years 11 months 23 days
Weighted-Average Remaining Contractual Term, Exercisable	4 years 10 months 21 days
Aggregate Intrinsic Value, Outstanding Beginning balance	$ 5,096,000
Aggregate Intrinsic Value, Outstanding Ending balance	5,572,000	5,096,000
Aggregate Intrinsic Value, Vested or expected to vest	5,566,000
Aggregate Intrinsic Value, Exercisable	5,376,000
2013 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding Options, Beginning balance	949,589
Outstanding Options, granted	485,900
Outstanding Options, forfeited	0
Outstanding Options, Ending balance	1,435,489	949,589
Vested or expected to vest outstanding options	1,427,558
Exercisable outstanding options	203,631
Weighted-Average Exercise Price, Outstanding Beginning balance	$ 8.88
Weighted-Average Exercise Price, Options granted	$ 7.18
Weighted-Average Exercise Price, Options forfeited	$ 0
Weighted-Average Exercise Price, Outstanding Ending balance	$ 8.30	$ 8.88
Weighted-Average Exercise Price, Vested or expected to vest	$ 8.30
Weighted-Average Exercise Price, Exercisable	$ 8.03
Weighted-Average Remaining Contractual Term, Outstanding	9 years 1 month 28 days	9 years 1 month 2 days
Weighted-Average Remaining Contractual Term, Vested or expected to vest	9 years 1 month 28 days
Weighted-Average Remaining Contractual Term, Exercisable	8 years 9 months 11 days
Aggregate Intrinsic Value, Outstanding Beginning balance	12,000
Aggregate Intrinsic Value, Outstanding Ending balance	851,000	12,000
Aggregate Intrinsic Value, Vested or expected to vest	845,000
Aggregate Intrinsic Value, Exercisable	$ 65,000

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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-Publisher FASB

-Name Accounting Standards Codification

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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

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

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

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

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

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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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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of fully vested and expected to vest options that are exercisable.

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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

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

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

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

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