Marketable Securities and Investments (Schedule of Activity of Major Classes of Assets Measured at Fair Value Using Level 3 Inputs) (Details) (USD $) In Thousands	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		$ 254,119
Redemptions of securities		(109,700)
Unrealized gains included in accumulated other comprehensive income (loss), net		5,721
Unrealized gain (loss) included in the statement of operations		9,614
Ending balance		150,140
Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	137,256	244,505
Redemptions of securities	(15,450)	(109,700)
Unrealized gains included in accumulated other comprehensive income (loss), net	(3,031)	5,721
Unrealized gain (loss) included in the statement of operations		9,614
Ending balance	118,775	150,140
Auction Rate Securities [Member] \| Put Option Related to Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		9,614
Unrealized gain (loss) included in the statement of operations		(9,614)
Ending balance		0
Put Option Related to Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Unrealized gain (loss) included in the statement of operations		$ (9,614)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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- Definition

This element represents total gains or losses for the period (realized and unrealized), arising from assets measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in earnings or resulted in a change in net asset value.

+ 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(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258

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- Definition

This element represents total gains or losses for the period (realized and unrealized), arising from assets measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in other comprehensive income (a separate component of shareholders' equity).

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- Definition

This element represents purchases, sales, issuances, and settlements (net) which have taken place during the period in relation to assets measured at fair value on a recurring basis using unobservable inputs (Level 3).

+ References

+ Details

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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 Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c

-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 2: 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=6925170&loc=d3e19207-110258

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