Investments (Asset-Backed Securities In Gross Unrealized Loss Position By Ratings Distribution) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 39,133	$ 38,368
Estimated Fair Value	42,199	40,967
Gross Unrealized Losses	419	626
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,722
Estimated Fair Value	2,546
Gross Unrealized Losses	176
Asset-Backed Securities [Member] \| U.S. Government, Government Agencies And Government-Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	852
Estimated Fair Value	810
Gross Unrealized Losses	42
Asset-Backed Securities [Member] \| AAA [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	246
Estimated Fair Value	239
Gross Unrealized Losses	7
Asset-Backed Securities [Member] \| AA [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	226
Estimated Fair Value	215
Gross Unrealized Losses	11
Asset-Backed Securities [Member] \| A [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	294
Estimated Fair Value	286
Gross Unrealized Losses	8
Asset-Backed Securities [Member] \| BBB [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	209
Estimated Fair Value	193
Gross Unrealized Losses	16
Asset-Backed Securities [Member] \| Non-Investment Grade [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	895
Estimated Fair Value	803
Gross Unrealized Losses	$ 92

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.

+ References+ Details

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