Investments (Amortized Cost, Gross Unrealized Gains and Losses and Estimated Fair Value) (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Current Investments [Member] \| All Other Corporate [Member]
Amortized Cost	$ 9,694	$ 6,277
Gross Unrealized Gains	345	300
Gross Unrealized Losses		5
Estimated Fair Value	10,039	6,572
Current Investments [Member] \| U.S. Government and Agencies [Member]
Amortized Cost	603,503	246,996
Gross Unrealized Gains	38	21
Gross Unrealized Losses	4
Estimated Fair Value	603,537	247,017
Current Investments [Member] \| Debt Securities [Member]
Amortized Cost	613,197	253,273
Gross Unrealized Gains	383	321
Gross Unrealized Losses	4	5
Estimated Fair Value	613,576	253,589
Non-current Investments [Member] \| U.S. Government and Agencies [Member]
Amortized Cost	7,344	7,806
Gross Unrealized Gains	3
Gross Unrealized Losses	13	90
Estimated Fair Value	7,334	7,716
Non-current Investments [Member] \| Equity Securities [Member]
Amortized Cost	750,767	776,934
Gross Unrealized Gains	1,278,496	1,866,165
Gross Unrealized Losses	597	492
Estimated Fair Value	2,028,666	2,642,607
Non-current Investments [Member] \| Common Stock Banks, Trusts and Insurance Companies [Member]
Amortized Cost	20,573	16,340
Gross Unrealized Gains	35,229	32,936
Gross Unrealized Losses	497
Estimated Fair Value	55,305	49,276
Non-current Investments [Member] \| Common Stock Industrial, Miscellaneous and All Other [Member]
Amortized Cost	730,194	760,594
Gross Unrealized Gains	1,243,267	1,833,229
Gross Unrealized Losses	100	492
Estimated Fair Value	1,973,361	2,593,331
Non-current Investments [Member] \| Debt Securities [Member]
Amortized Cost	1,305,668	1,014,723
Gross Unrealized Gains	14,648	11,481
Gross Unrealized Losses	2,454	2,572
Estimated Fair Value	1,317,862	1,023,632
Non-current Investments [Member] \| US Government-Sponsored Enterprises [Member]
Amortized Cost	1,064,797	815,066
Gross Unrealized Gains	12,644	10,564
Gross Unrealized Losses	1,523	2,247
Estimated Fair Value	1,075,918	823,383
Non-current Investments [Member] \| Corporate Debt Securities [Member]
Amortized Cost	233,527	191,851
Gross Unrealized Gains	2,001	917
Gross Unrealized Losses	918	235
Estimated Fair Value	234,610	192,533
Non-current Investments Available for Sale [Member]
Amortized Cost	2,056,435	1,791,657
Gross Unrealized Gains	1,293,144	1,877,646
Gross Unrealized Losses	3,051	3,064
Estimated Fair Value	$ 3,346,528	$ 3,666,239

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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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.

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