Summary of Significant Accounting Policies and Recent Accounting Pronouncements - Additional Information (Detail) (USD $)	12 Months Ended
Dec. 31, 2014 Segment	Dec. 31, 2013	Dec. 31, 2012
Summary Of Significant Accounting Policies [Line Items]
Number of operating segments	1us-gaap_NumberOfOperatingSegments
Accrued liabilities	$ 17,366,000us-gaap_AccruedLiabilitiesCurrent	$ 14,601,000us-gaap_AccruedLiabilitiesCurrent
Accrued employee compensation		5,000,000us-gaap_AccruedEmployeeBenefitsCurrent
Net decrease in other assets	(34,013,000)	1,618,000	(2,507,000)
Government receivables unbilled amount	2,400,000	2,400,000
Deferred revenue	3,300,000us-gaap_DeferredRevenue
Rent expense and occupancy costs	4,400,000us-gaap_LeaseAndRentalExpense	3,400,000us-gaap_LeaseAndRentalExpense	2,600,000us-gaap_LeaseAndRentalExpense
Accounts Payable [Member]
Summary Of Significant Accounting Policies [Line Items]
Accrued liabilities		9,600,000
Employee Stock Purchase Plan [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of closing price of common stock	85.00%
Percentage of discount recognized on graded-vesting based on stock-based compensation expense over the purchase period	15.00%
Patents [Member]
Summary Of Significant Accounting Policies [Line Items]
Patent amortization expense	500,000	400,000	600,000
Initial term of patents	20 years
Patents [Member] \| Research and Development Expenses [Member]
Summary Of Significant Accounting Policies [Line Items]
Book value of patent abandoned	$ 100,000	$ 500,000	$ 400,000

Percentage of closing price at which employees can purchase common stock under the ESPP.

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Carrying value as of the balance sheet date of obligations, excluding pension and other postretirement benefits, incurred through that date and payable for perquisites provided to employees pertaining to services received from them. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20

-Article 5

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Current Liabilities

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-Topic 210

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-Section S99

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-Subparagraph (SX 210.5-02.20)

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Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

+ References

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-Name Accounting Standards Codification

-Topic 230

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-Paragraph 28

-Subparagraph (b)

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-Topic 350

-SubTopic 30

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-Topic 350

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-Paragraph 2

-Subparagraph (a)(2)

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Amount of deferred revenue as of balance sheet date. Deferred revenue represents collections of cash or other assets related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

+ References

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

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 13

-Section A

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-Name Accounting Standards Codification

-Topic 605

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 13.A.4(a).Q1 Response)

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Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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- Definition

Unbilled amounts (net of unliquidated progress payments) of government contract receivables.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 912

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The increase (decrease) during the reporting period in other assets used in operating activities not separately disclosed in the statement of cash flows. May include changes in other current assets, other noncurrent assets, or a combination of other current and noncurrent assets.

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Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

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- Definition

The carrying amount on the books of the entity of the asset to be abandoned.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 35

-Paragraph 47

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Discount rate from fair value on purchase date that participants pay for shares.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

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