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Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015 USD ($) Segment	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Accounting Policy [Line Items]
Number of operating segment | Segment	1
Highly liquid investment maturity period	three months or less
Restricted cash	$ 7,254,000	$ 7,254,000
Cash and cash equivalents	$ 153,324,000	$ 165,455,000	$ 76,332,000	$ 38,872,000
Long term Investments Maturity	12 months
Short term investments Maturity	12 months
Impairment of long-lived assets	$ 0
Minimum [Member] | Computer Equipment [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life	3 years
Minimum [Member] | Laboratory Equipment [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life	3 years
Minimum [Member] | Furniture and Fixtures [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life	3 years
Maximum [Member] | Computer Equipment [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life	5 years
Maximum [Member] | Laboratory Equipment [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life	5 years
Maximum [Member] | Furniture and Fixtures [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life	5 years
Foreign subsidiaries [Member]
Accounting Policy [Line Items]
Cash and cash equivalents	$ 27,200,000

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Accounting policy.

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Cash
-URI http://asc.fasb.org/extlink&oid=6506951

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3044-108585

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Cash Equivalents
-URI http://asc.fasb.org/extlink&oid=6507016

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Section S99
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The aggregate amount of write-downs for impairments recognized during the period for long-lived assets held for abandonment, exchange or sale.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=51824106&loc=d3e2611-110228

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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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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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Cash and equivalents whose use in whole or in part is restricted for the long-term, generally by contractual agreements or regulatory requirements.

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