Fair Value Measurements - Assets and liabilities measured at fair value (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015
Estimate of Fair Value
Assets:
Cash and cash equivalents - money market funds	$ 35,613
Short term investments - bond mutual funds	15,591
Assets, fair value disclosure	51,204
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents - money market funds	35,613
Short term investments - bond mutual funds	15,591
Assets, fair value disclosure	51,204
Significant Other Observable Inputs (Level 2)
Assets:
Cash and cash equivalents - money market funds
Short term investments - bond mutual funds
Assets, fair value disclosure
Significant Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents - money market funds
Short term investments - bond mutual funds
Assets, fair value disclosure

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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

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

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

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-Section 50

-Paragraph 5

-Subparagraph (aa)

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-Publisher FASB

-Name Accounting Standards Codification

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Fair value portion 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.

+ 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

-Glossary Cash Equivalents

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