Stock Compensation Plans - Additional Information (Detail) - USD ($)	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant	345,486
Release of repurchase liability for shares vested	$ 23,000	$ 26,000
Weighted-average grant date fair value of stock options granted (usd per share)	$ 6.04	$ 17.87
Compensation cost related to unvested employee stock option awards	$ 5,500,000
Remaining weighted-average vesting period	2 years 1 month 2 days
Non-Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost related to unvested employee stock option awards	$ 581,000
Remaining weighted-average vesting period	2 years 1 month 6 days
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period from grant date	10 years
2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock for annual increase in shares available for issuance	1,200,000
Percentage of outstanding shares of common stock for annual increase in shares available for issuance	3.00%
Shares available for grant	345,486
2014 Plan [Member] \| Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting under Equity Incentive Plans, term	4 years
2012 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock exercised	74,970
Common stock options vested in the period	11,512
Release of repurchase liability for shares vested	$ 23,000
Stock option repurchase liability	$ 0
Share-Based Compensation Arrangement By Share-Based Payment Award, Options, Exercised Prior To Vesting, Number Of Shares Repurchased	0
2012 Plan [Member] \| Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting under Equity Incentive Plans, term	4 years

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=6415400&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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- Definition

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=6415400&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

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.

+ 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=6415400&loc=d3e5070-113901

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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=6415400&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=6415400&loc=d3e5070-113901

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- Definition

Number of options vested.

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- Definition

Release of repurchase liability for stock options shares vested during period.

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Repurchase Liability For Early Exercise Of Stock Options

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Share Based Compensation Annual Increase In Number Of Shares

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- Definition

Share-Based Compensation Arrangement By Share-Based Payment Award, Options, Exercised Prior To Vesting, Number Of Shares Repurchased

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- Definition

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

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