Investments (States, Municipalities And Political Subdivisions Securities In A Gross Unrealized Loss Position by Ratings Distribution) (Details) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 38,079	$ 37,656
Estimated Fair Value	40,604	38,900
Gross Unrealized Losses	649	851
States, Municipalities And Political Subdivisions [Member] \| AAA [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	198
Estimated Fair Value	190
Gross Unrealized Losses	8
States, Municipalities And Political Subdivisions [Member] \| AA [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	485
Estimated Fair Value	378
Gross Unrealized Losses	107
States, Municipalities And Political Subdivisions [Member] \| A [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	370
Estimated Fair Value	340
Gross Unrealized Losses	30
States, Municipalities And Political Subdivisions [Member] \| BBB [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	67
Estimated Fair Value	63
Gross Unrealized Losses	4
States, Municipalities And Political Subdivisions [Member] \| Non-Investment Grade [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	16
Estimated Fair Value	15
Gross Unrealized Losses	1
Total States, Municipalities And Political Subdivisions Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,136
Estimated Fair Value	986
Gross Unrealized Losses	$ 150

- 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