Available-For-Sale Securities (Summary Of Available-For-Sale Debt And Equity Securities At Estimated Fair Value) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total	$ 4,971,259	$ 4,925,704
Gross Unrealized Gains	32,852	33,154
Gross Unrealized Losses	(42,098)	(9,720)
Estimated Fair Value, Debt securities	4,956,746	4,944,507
Estimated Fair Value, Equity securities	5,267	4,631
Estimated Fair Value, Total	4,962,013	4,949,138
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Debt securities	4,969,808	4,924,253
Gross Unrealized Gains	29,036	29,974
Gross Unrealized Losses	(42,098)	(9,720)
Estimated Fair Value, Debt securities	4,956,746	4,944,507
Debt Securities [Member] \| U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Debt securities	1,147,146	1,349,348
Gross Unrealized Gains	8,505	7,109
Gross Unrealized Losses	(322)	(1,020)
Estimated Fair Value, Debt securities	1,155,329	1,355,437
Debt Securities [Member] \| Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Debt securities	372,260	520,063
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value, Debt securities	372,260	520,063
Debt Securities [Member] \| U.S. Government Agencies And FDIC Guaranteed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Debt securities	1,082,230	1,284,654
Gross Unrealized Gains	8,593	11,919
Gross Unrealized Losses	(236)	(463)
Estimated Fair Value, Debt securities	1,090,587	1,296,110
Debt Securities [Member] \| Municipal Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Debt securities	24,410	17,543
Gross Unrealized Gains	183	103
Gross Unrealized Losses	(2)	(21)
Estimated Fair Value, Debt securities	24,591	17,625
Debt Securities [Member] \| Non-U.S. Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Debt securities	266,234	286,410
Gross Unrealized Gains	1,450	1,880
Gross Unrealized Losses	(30,606)	(86)
Estimated Fair Value, Debt securities	237,078	288,204
Debt Securities [Member] \| Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Debt securities	1,698,857	1,112,976
Gross Unrealized Gains	9,242	8,040
Gross Unrealized Losses	(4,231)	(1,762)
Estimated Fair Value, Debt securities	1,703,868	1,119,254
Debt Securities [Member] \| Residential Mortgage And Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Debt securities	317,371	277,359
Gross Unrealized Gains	1,063	923
Gross Unrealized Losses	(1,908)	(1,239)
Estimated Fair Value, Debt securities	316,526	277,043
Debt Securities [Member] \| Student Loan-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Debt securities	61,300	75,900
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(4,793)	(5,129)
Estimated Fair Value, Debt securities	56,507	70,771
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Equity securities	1,451	1,451
Gross Unrealized Gains	3,816	3,180
Gross Unrealized Losses	0	0
Estimated Fair Value, Equity securities	$ 5,267	$ 4,631

For an unclassified balance sheet, total of debt securities categorized neither as held-to-maturity nor trading.

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+ Details

- Definition

For an unclassified balance sheet, this item represents equity securities categorized neither as held-to-maturity nor trading.

+ References

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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