Cash, Cash Equivalents, Restricted Cash, and Short-term Investments - Summary of Cash, Cash Equivalents, Restricted Cash, and Short-term Investments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash and Cash Equivalents [Abstract]
Cash	$ 1,511us-gaap_Cash	$ 930us-gaap_Cash
Money market	33,255us-gaap_MoneyMarketFundsAtCarryingValue	9,084us-gaap_MoneyMarketFundsAtCarryingValue
Total cash and cash equivalents	34,766	10,014	8,896
Corporate bonds		6,191us-gaap_MarketableSecuritiesCurrent
Total short-term investments		6,191us-gaap_ShortTermInvestments
Total restricted cash	250	375
Total	$ 35,016us-gaap_AssetsFairValueDisclosure	$ 16,580us-gaap_AssetsFairValueDisclosure

Cash, Cash Equivalents, Restricted Cash, and Short-term Investments - Summary of Cash, Cash Equivalents, Restricted Cash, and Short-term Investments (Detail) (USD $)
In Thousands, unless otherwise specified

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Cash and Cash Equivalents [Abstract]

Cash

$ 1,511us-gaap_Cash

$ 930us-gaap_Cash

Money market

33,255us-gaap_MoneyMarketFundsAtCarryingValue

9,084us-gaap_MoneyMarketFundsAtCarryingValue

Total cash and cash equivalents

34,766us-gaap_CashAndCashEquivalentsAtCarryingValue

10,014us-gaap_CashAndCashEquivalentsAtCarryingValue

8,896us-gaap_CashAndCashEquivalentsAtCarryingValue

Corporate bonds

6,191us-gaap_MarketableSecuritiesCurrent

Total short-term investments

6,191us-gaap_ShortTermInvestments

Total restricted cash

250us-gaap_RestrictedCashAndCashEquivalents

375us-gaap_RestrictedCashAndCashEquivalents

Total

$ 35,016us-gaap_AssetsFairValueDisclosure

$ 16,580us-gaap_AssetsFairValueDisclosure

- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

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- Definition

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

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-URI http://asc.fasb.org/extlink&oid=6506951

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-Publisher FASB

-Name Accounting Standards Codification

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-URI http://asc.fasb.org/extlink&oid=6507016

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 1

-Article 5

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.1)

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-Topic 230

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- Definition

Amount of investments in debt and equity securities, including, but not limited to, held-to-maturity, trading and available-for-sale expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer.

+ References

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

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-Name Accounting Standards Codification

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- Definition

Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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- Definition

The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. This element is for unclassified presentations; for classified presentations there is a separate and distinct element.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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-Paragraph 1

-Article 5

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-Publisher FASB

-Name Accounting Standards Codification

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- Definition

Investments which are intended to be sold in the short term (usually less than one year or the normal operating cycle, whichever is longer) including trading securities, available-for-sale securities, held-to-maturity securities, and other short-term investments not otherwise listed in the existing taxonomy.

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