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Cash Equivalents and Investments (Details) (USD $)			6 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2011 Maximum [Member] years	Jun. 30, 2011 Minimum [Member] years	Jun. 30, 2011 Money Market Funds [Member]	Dec. 31, 2010 Money Market Funds [Member]	Jun. 30, 2011 Municipal Debt Securities [Member]	Dec. 31, 2010 Municipal Debt Securities [Member]	Jun. 30, 2011 Federal Home Loan Securities [Member]	Dec. 31, 2010 Federal Home Loan Securities [Member]	Jun. 30, 2011 Certificates of Deposit [Member]	Dec. 31, 2010 Certificates of Deposit [Member]
Money market fund at fair value					$ 21,600,000	$ 11,700,000
Short term investment maturity period			1
Long term investment maturity period			5	1
Short-Term investments	10,975,000	17,381,000					10,735,000	16,901,000			240,000	480,000
Long-Term investments	$ 25,666,000	$ 27,393,000					$ 15,600,000	$ 11,327,000	$ 10,066,000	$ 16,066,000

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Long Term Investment Maturity Period

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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means 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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
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-Paragraph 7, 8, 9, 10
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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This item represents investments in debt securities which are categorized as held-to-maturity and that have scheduled maturities within one year of the balance sheet date or the normal operating cycle, whichever is longer; such investments are measured at amortized cost (carrying value). The held-to-maturity category is for those securities that the Entity has the positive intent and ability to hold until maturity.

+ References

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-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 43
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
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+ References

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