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

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

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Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

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Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1.

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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.

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Fair Value of Financial Instruments (Details 3) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Fair value hierarchy for its financial assets
Transfer of assets between Level 1 to Level 2	$ 0	$ 0
Transfer of liabilities between Level 1 to Level 2	0	0
Transfer of assets between Level 2 to Level 1	0	0
Transfer of liabilities between Level 2 to Level 1	0	0
Fair Value
Fair value hierarchy for its financial assets
Money market funds	5,002		1,837
Total assets	39,898		25,168
Fair Value \| U.S. government-sponsored enterprise bonds
Fair value hierarchy for its financial assets
Available-for-sale securities	9,707		2,248
Fair Value \| Municipal Bonds
Fair value hierarchy for its financial assets
Available-for-sale securities	4,205		1,243
Fair Value \| Corporate notes
Fair value hierarchy for its financial assets
Available-for-sale securities	17,431		17,164
Fair Value \| Certificates of deposit
Fair value hierarchy for its financial assets
Available-for-sale securities	2,954		2,676
Fair Value \| Commercial Paper
Fair value hierarchy for its financial assets
Available-for-sale securities	599
Level 1
Fair value hierarchy for its financial assets
Money market funds	5,002		1,837
Total assets	5,002		1,837
Level 2
Fair value hierarchy for its financial assets
Total assets	34,896		23,331
Level 2 \| U.S. government-sponsored enterprise bonds
Fair value hierarchy for its financial assets
Available-for-sale securities	9,707		2,248
Level 2 \| Municipal Bonds
Fair value hierarchy for its financial assets
Available-for-sale securities	4,205		1,243
Level 2 \| Corporate notes
Fair value hierarchy for its financial assets
Available-for-sale securities	17,431		17,164
Level 2 \| Certificates of deposit
Fair value hierarchy for its financial assets
Available-for-sale securities	2,954		2,676
Level 2 \| Commercial Paper
Fair value hierarchy for its financial assets
Available-for-sale securities	$ 599