Investments (Distribution Of Contractual Maturity Available For Sale) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 7,394	$ 8,810
Amortized Cost	7,306	9,025
Fixed-Maturity Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Due in one year or less, Fair Value	872
Due after one year through five years, Fair Value	862
Due after five years through ten years, Fair Value	703
Due after ten years through fifteen years, Fair Value	462
Due after fifteen years, Fair Value	1,677
Fair Value	6,163	7,336
Due in one year or less, Amortized Cost	870
Due after one year through five years, Amortized Cost	834
Due after five years through ten years, Amortized Cost	667
Due after ten years through fifteen years, Amortized Cost	438
Due after fifteen years, Amortized Cost	1,564
Amortized Cost	6,044	7,492
Mortgage-Backed Securities [Member] \| Fixed-Maturity Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,294
Amortized Cost	1,275
Asset-Backed Securities [Member] \| Fixed-Maturity Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	293
Amortized Cost	396
Variable Interest Entity [Member] \| Fixed-Maturity Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Due in one year or less, Fair Value	7
Due after one year through five years, Fair Value	132
Due after ten years through fifteen years, Fair Value	75
Due after fifteen years, Fair Value	2
Fair Value	428
Due in one year or less, Amortized Cost	7
Due after one year through five years, Amortized Cost	124
Due after ten years through fifteen years, Amortized Cost	81
Due after fifteen years, Amortized Cost	2
Amortized Cost	458
Variable Interest Entity [Member] \| Mortgage-Backed Securities [Member] \| Fixed-Maturity Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	87
Amortized Cost	106
Variable Interest Entity [Member] \| Asset-Backed Securities [Member] \| Fixed-Maturity Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	125
Amortized Cost	$ 138

Available For Sale Securities, Debt Maturities, Due After Fifteen Years, Amortized Cost

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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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Amount of available-for-sale debt securities at cost, net of adjustments, maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

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Amount of available-for-sale debt securities at cost, net of adjustments, maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

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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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