Fair Value of Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Short-term investments	$ 29,856	$ 33,574
Long-term investments	1,408	26,997
Short-term investments
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Short-term investments	29,856	33,574
Short-term investments \| Corporate bonds
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Short-term investments	22,591	24,575
Short-term investments \| Municipal bonds
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Short-term investments	7,265	5,025
Short-term investments \| Commercial paper
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Short-term investments		3,974
Long-term investments
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Long-term investments	1,408	26,997
Long-term investments \| Corporate bonds
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Long-term investments		21,186
Long-term investments \| Municipal bonds
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Long-term investments	1,408	5,811
Fair value on a recurring basis
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Long-term investments		5,811
Total Assets	52,911	86,627
Fair value on a recurring basis \| Money market funds
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Money market funds	21,647	26,056
Fair value on a recurring basis \| Short-term investments \| Corporate bonds
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Short-term investments	22,591	24,575
Fair value on a recurring basis \| Short-term investments \| Municipal bonds
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Short-term investments	7,265	5,025
Fair value on a recurring basis \| Short-term investments \| Commercial paper
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Short-term investments		3,974
Fair value on a recurring basis \| Long-term investments \| Corporate bonds
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Long-term investments		21,186
Fair value on a recurring basis \| Long-term investments \| Municipal bonds
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Long-term investments	1,408
Level 1 \| Fair value on a recurring basis
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Assets	21,647	26,056
Level 1 \| Fair value on a recurring basis \| Money market funds
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Money market funds	21,647	26,056
Level 2 \| Fair value on a recurring basis
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Long-term investments		5,811
Total Assets	31,264	60,571
Level 2 \| Fair value on a recurring basis \| Short-term investments \| Corporate bonds
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Short-term investments	22,591	24,575
Level 2 \| Fair value on a recurring basis \| Short-term investments \| Municipal bonds
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Short-term investments	7,265	5,025
Level 2 \| Fair value on a recurring basis \| Short-term investments \| Commercial paper
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Short-term investments		3,974
Level 2 \| Fair value on a recurring basis \| Long-term investments \| Corporate bonds
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Long-term investments		$ 21,186
Level 2 \| Fair value on a recurring basis \| Long-term investments \| Municipal bonds
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Long-term investments	$ 1,408

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
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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Amount of investment in debt and equity securities categorized neither as trading securities nor held-to-maturity securities and intended be sold or mature one year or operating cycle, if longer.

+ 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)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26626-111562

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Investments in debt and equity securities which are categorized neither as held-to-maturity nor trading and which are intended to be sold or mature more than one year from the balance sheet date or operating cycle, if longer. Such securities are reported at fair value; unrealized gains (losses) related to Available-for-sale Securities are excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain (loss) of an Available-for-sale security that is designated as being hedged in a fair value hedge is recognized in earnings during the period of the hedge, as are other than temporary declines in fair value below the cost basis for investments in equity securities and debt securities that an entity intends to sell or it is more likely than not that it will be required to sell before the recovery of its amortized cost basis. Other than temporary declines in fair value below the cost basis for debt securities categorized as Available-for-sale that an entity does not intend to sell and for which it is not more likely than not that the entity will be required to sell before the recovery of its amortized cost basis are bifurcated into credit losses and losses related to all other factors. Other than temporary declines in fair value below cost basis related to credit losses are recognized in earnings, and losses related to all other factors are recognized in other comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Available-for-Sale Securities
-URI http://asc.fasb.org/extlink&oid=6505594

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26626-111562

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

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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