Stock-Based Compensation - Additional Information (Detail) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options for every share issued	1.75
Percentage of fair market value on the purchase date	85.00%
Maximum number of shares per employee	2,000
Employee stock purchase plan offering period	6 months
Maximum value of shares per employee	$ 25,000
Common stock reserved for issuance	1,000,000
Shares purchased by employee since inception of ESPP	557,738
Shares purchased under ESPP	38,298	36,921
Expected dividend yield in option-pricing model	0.00%
Unrecognized compensation cost	$ 7,400,000
Market Condition Based Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based payment award expiration period (years)	7 years
Unrecognized compensation cost, recognized over an estimated weighted-average period (years)	3 years 2 months 1 day
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based payment award vesting period (years)	4 years
Stock Options [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based payment award expiration period (years)	10 years
Stock Options [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based payment award expiration period (years)	5 years
Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based payment award vesting period (years)	1 year
Unrecognized compensation cost, recognized over an estimated weighted-average period (years)	1 year 4 months 28 days
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based payment award vesting period (years)	3 years
Unrecognized compensation cost, recognized over an estimated weighted-average period (years)	5 months 5 days
Standard Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost, recognized over an estimated weighted-average period (years)	2 years 11 months 12 days

The reduction in number of available shares when a share is issued under the share based compensation.

No definition available.

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- Definition

The estimated dividend rate (a percentage of the share price) used in option-pricing model.

+ References

No definition available.

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- Definition

The highest value of shares that an employee can purchase under the plan per period.

+ References

No definition available.

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- Definition

The offering period of the employee stock purchase plan ("ESPP").

+ References

No definition available.

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- Definition

The number of shares purchased by employees since inception of ESPP.

+ References

No definition available.

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- Definition

Aggregate number of common shares reserved for future issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.29)

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- Definition

Unrecognized cost of unvested share-based compensation awards.

+ 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 (i)

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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.

+ References

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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

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

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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

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-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(2)

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- Definition

The highest quantity of shares an employee can purchase under the plan per period.

+ References

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- Definition

Purchase price of common stock expressed as a percentage of its fair value.

+ References

No definition available.

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- Definition

The number of shares purchased on the open market during the period for issuance to employees under the plan.

+ 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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