Marketable Securities and Investments (Marketable Securities) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	$ 852,027	$ 1,024,385
Gross unrealized gains, trading securities	969	1,552
Gross unrealized losses	(17,600)	(14,401)
Short-term marketable securities	331,967	375,005
Long-term marketable securities	503,429	636,531
Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	96	96
Gross unrealized gains, trading securities	0	0
Gross unrealized losses	0	0
Short-term marketable securities	51	51
Long-term marketable securities	45	45
Certificates of Deposit [Member] \| Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate Fair value	96	96
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	59,989	59,912
Gross unrealized gains, trading securities	0	34
Gross unrealized losses	(23)	(2)
Short-term marketable securities	59,966	59,944
Long-term marketable securities	0	0
Commercial Paper [Member] \| Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate Fair value	59,966	59,944
U.S. Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	539,365	651,855
Gross unrealized gains, trading securities	867	1,416
Gross unrealized losses	(995)	(736)
Short-term marketable securities	261,922	301,625
Long-term marketable securities	277,315	350,910
U.S. Corporate Debt Securities [Member] \| Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate Fair value	539,237	652,535
U.S. Government Agencies Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	117,227	161,722
Gross unrealized gains, trading securities	102	102
Gross unrealized losses	(7)	(119)
Short-term marketable securities	10,028	13,385
Long-term marketable securities	107,294	148,320
U.S. Government Agencies Obligations [Member] \| Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate Fair value	117,322	161,705
Auction Rate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	135,350	150,800
Gross unrealized gains, trading securities	0	0
Gross unrealized losses	(16,575)	(13,544)
Aggregate Fair value	118,775	137,256
Short-term marketable securities	0	0
Long-term marketable securities	118,775	137,256
Auction Rate Securities [Member] \| Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate Fair value	118,775	137,256
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate Fair value	$ 835,396	$ 1,011,536

Investments in debt and equity securities which are categorized neither as trading securities nor held-to-maturity securities and which are intended be sold or mature within one year from the balance sheet date or the normal operating cycle, whichever is 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.

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-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 43

-Chapter 3

-Section A

-Paragraph 4, 5

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+ Details

- 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 represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

+ References+ Details

- Definition

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

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

-Publisher FASB

-Name Accounting Standards Codification

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+ Details