Fair Value Measurements (Details 2) (Auction Rate Securities, USD $)	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Summary of changes in fair value of the auction rate securities
Unrealized loss on auction rate securities			$ 200,000
Fair Value, Measurements, Recurring \| Level 3
Summary of changes in fair value of the auction rate securities
Fair value at beginning of period	8,178,000	22,384,000	8,323,000	22,102,000
Redemptions	(2,700,000)		(2,900,000)
Change in valuation	(27,000)	565,000	28,000	847,000
Fair value at end of period	$ 5,451,000	$ 22,949,000	$ 5,451,000	$ 22,949,000

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Represents the quantification of the effect of changes in the valuation technique and related inputs, during the period, used to measure the liability at fair value as of the statement of financial position reporting date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 65

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=7488894&loc=SL6595801-161440

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- Definition

Amount of gain (loss) recognized in other comprehensive income, arising from assets measured at fair value on a recurring basis using unobservable inputs (level 3).

+ References

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- Definition

Amount of purchases, sales, issues, and settlements (net) which have taken place in relation to assets measured at fair value on a recurring basis using unobservable inputs (level 3).

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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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- Definition

This element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

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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.

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