Marketable Investments (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Marketable investments classified as held-to-maturity:
Amortized Cost	$ 600,326	$ 507,399
Gross Unrealized Gains	201	196
Gross Unrealized Losses	(609)	(220)
Fair Value	599,918	507,375
Government-sponsored enterprises
Marketable investments classified as held-to-maturity:
Amortized Cost	262,937	282,005
Gross Unrealized Gains	117	52
Gross Unrealized Losses	(112)	(152)
Fair Value	262,942	281,905
Corporate notes and bonds
Marketable investments classified as held-to-maturity:
Amortized Cost	337,389	225,394
Gross Unrealized Gains	84	144
Gross Unrealized Losses	(497)	(68)
Fair Value	$ 336,976	$ 225,470

For an unclassified balance sheet, this item represents investments in debt securities which are categorized as held-to-maturity. The held-to-maturity category is for those securities that the entity has the positive intent and ability to hold until maturity.

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

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Reference 7: http://www.xbrl.org/2003/role/presentationRef

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+ Details