Fair Value Measurement - Additional Information (Detail) - USD ($)	Sep. 30, 2015	Dec. 31, 2014
Fair Value Inputs Assets Quantitative Information [Line Items]
Cash balance	$ 70,100,000
Cash equivalents	38,900,000
Short-term investments	10,117,000	$ 8,730,000
Long term investments	0
Money Market Funds
Fair Value Inputs Assets Quantitative Information [Line Items]
Available-for-sale securities	$ 30,400,000	$ 30,400,000

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

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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. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References

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

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-Glossary Cash

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

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Amount of 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

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The total amount of investments that are intended to be held for an extended period of time (longer than one operating cycle).

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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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-Name Regulation S-X (SX)

-Number 210

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