Investments (Available-For-Sale Investments, Including Accrued Interest) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Amortized Cost	$ 576,519	$ 770,574
Gross Unrealized Gains	6,639	8,207
Gross Unrealized Losses	(1,100)	(1,090)
Marketable securities, Fair Value	502,137	282,016
Marketable securities, non-current, Fair Value		416,165
Total, Fair Value	582,058	777,691
Residential Mortgage-Backed Securities [Member] \| Marketable Securities [Member]
Amortized Cost	90,422	53,944
Gross Unrealized Gains	1,449	787
Gross Unrealized Losses	(41)	(13)
Marketable securities, Fair Value	91,830	54,718
Residential Mortgage-Backed Securities [Member] \| Marketable Securities, Non-Current [Member]
Amortized Cost		79,605
Gross Unrealized Gains		1,161
Gross Unrealized Losses		(20)
Marketable securities, non-current, Fair Value		80,746
Residential Mortgage-Backed Securities [Member] \| Restricted Investments [Member]
Amortized Cost	7,768	6,368
Gross Unrealized Gains	44	128
Gross Unrealized Losses	(11)
Restricted assets, Fair Value	7,801	6,496
Asset-Backed Securities [Member] \| Marketable Securities [Member]
Amortized Cost	65,257	12,983
Gross Unrealized Gains	81	5
Gross Unrealized Losses	(6)
Marketable securities, Fair Value	65,332	12,988
Asset-Backed Securities [Member] \| Marketable Securities, Non-Current [Member]
Amortized Cost		58,822
Gross Unrealized Gains		84
Gross Unrealized Losses		(2)
Marketable securities, non-current, Fair Value		58,904
Asset-Backed Securities [Member] \| Restricted Investments [Member]
Amortized Cost	3,122	4,412
Gross Unrealized Gains	5	10
Gross Unrealized Losses
Restricted assets, Fair Value	3,127	4,422
Corporate Debt Securities [Member] \| Marketable Securities [Member]
Amortized Cost	325,872	125,708
Gross Unrealized Gains	4,638	1,655
Gross Unrealized Losses	(848)	(19)
Marketable securities, Fair Value	329,662	127,344
Corporate Debt Securities [Member] \| Marketable Securities, Non-Current [Member]
Amortized Cost		248,500
Gross Unrealized Gains		3,611
Gross Unrealized Losses		(881)
Marketable securities, non-current, Fair Value		251,230
Corporate Debt Securities [Member] \| Restricted Investments [Member]
Amortized Cost	50,139	45,931
Gross Unrealized Gains	337	620
Gross Unrealized Losses	(192)	(29)
Restricted assets, Fair Value	50,284	46,522
U.S. Treasury And Agencies [Member] \| Restricted Investments [Member]
Amortized Cost	1,300	1,302
Gross Unrealized Gains	5	10
Gross Unrealized Losses
Restricted assets, Fair Value	1,305	1,312
Government-Sponsored Enterprise Securities [Member] \| Marketable Securities [Member]
Amortized Cost	15,251	86,905
Gross Unrealized Gains	62	61
Gross Unrealized Losses
Marketable securities, Fair Value	15,313	86,966
Government-Sponsored Enterprise Securities [Member] \| Marketable Securities, Non-Current [Member]
Amortized Cost		25,402
Gross Unrealized Gains		3
Gross Unrealized Losses		(120)
Marketable securities, non-current, Fair Value		25,285
Government-Sponsored Enterprise Securities [Member] \| Restricted Investments [Member]
Amortized Cost	8,544	13,237
Gross Unrealized Gains	18	72
Gross Unrealized Losses	(2)	(6)
Restricted assets, Fair Value	8,560	13,303
Restricted Cash And Cash Equivalents [Member] \| Restricted Investments [Member]
Amortized Cost	8,844	7,455
Gross Unrealized Gains
Gross Unrealized Losses
Restricted assets, Fair Value	8,844	7,455
Marketable Securities [Member]
Amortized Cost	496,802	279,540
Gross Unrealized Gains	6,230	2,508
Gross Unrealized Losses	(895)	(32)
Marketable securities, Fair Value	502,137	282,016
Marketable Securities, Non-Current [Member]
Amortized Cost		412,329
Gross Unrealized Gains		4,859
Gross Unrealized Losses		(1,023)
Marketable securities, non-current, Fair Value		416,165
Restricted Investments [Member]
Amortized Cost	79,717	78,705
Gross Unrealized Gains	409	840
Gross Unrealized Losses	(205)	(35)
Restricted assets, Fair Value	$ 79,921	$ 79,510

For an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading.

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- Definition

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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+ 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.

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+ Details