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Investments (Amortized Cost And Fair Value Of Available-For-Sale and Held-To-Maturity Investment Portfolios) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Available For Sale Securities [Abstract]
Amortized Cost	$ 6,647		$ 6,122
Gross Unrealized Gains	120		251
Gross unrealized losses	(195)		(152)
Total Available-For-Sale, Fair Value	6,572		6,221
Other-Than-Temporary Impairments	(18)	[1]	(20)	[1]
Held To Maturity Securities [Abstract]
Amortized Cost	2,818		2,829
Gross Unrealized Gains	3		2
Gross Unrealized Losses	(131)		(157)
Total Held-To-Maturity, Fair Value	2,690		2,674
Other-Than-Temporary Impairments	0	[1]	0	[1]
State And Municipal Bonds [Member] | Variable Interest Entity Primary Beneficiary [Member]
Available For Sale Securities [Abstract]
Amortized Cost			38
Gross Unrealized Gains			3
Gross unrealized losses			0
Total Available-For-Sale, Fair Value			41
Other-Than-Temporary Impairments			0	[1]
Corporate Obligations [Member] | Variable Interest Entity Primary Beneficiary [Member]
Available For Sale Securities [Abstract]
Amortized Cost			177
Gross Unrealized Gains			9
Gross unrealized losses			(6)
Total Available-For-Sale, Fair Value			180
Other-Than-Temporary Impairments			0	[1]
Held To Maturity Securities [Abstract]
Amortized Cost	2,818		2,829
Gross Unrealized Gains	3		2
Gross Unrealized Losses	(131)		(157)
Total Held-To-Maturity, Fair Value	2,690		2,674
Other-Than-Temporary Impairments	0	[1]	0	[1]
Residential Mortgage-Backed Non-Agency [Member] | Variable Interest Entity Primary Beneficiary [Member]
Available For Sale Securities [Abstract]
Amortized Cost			92
Gross Unrealized Gains			0
Gross unrealized losses			(10)
Total Available-For-Sale, Fair Value			82
Other-Than-Temporary Impairments			0	[1]
Collateralized Debt Obligations [Member] | Variable Interest Entity Primary Beneficiary [Member]
Available For Sale Securities [Abstract]
Amortized Cost			97
Gross Unrealized Gains			0
Gross unrealized losses			(8)
Total Available-For-Sale, Fair Value			89
Other-Than-Temporary Impairments			0	[1]
Other Asset-Backed [Member] | Variable Interest Entity Primary Beneficiary [Member]
Available For Sale Securities [Abstract]
Amortized Cost			23
Gross Unrealized Gains			0
Gross unrealized losses			0
Total Available-For-Sale, Fair Value			23
Other-Than-Temporary Impairments			0	[1]
Money Market Securities [Member]
Available For Sale Securities [Abstract]
Amortized Cost	1,057		580
Gross Unrealized Gains	0		0
Gross unrealized losses	0		0
Total Available-For-Sale, Fair Value	1,057		580
Other-Than-Temporary Impairments	0	[1]	0	[1]
Money Market Securities [Member] | Variable Interest Entity Primary Beneficiary [Member]
Available For Sale Securities [Abstract]
Amortized Cost	321		210
Gross Unrealized Gains	0		0
Gross unrealized losses	0		0
Total Available-For-Sale, Fair Value	321		210
Other-Than-Temporary Impairments	0	[1]	0	[1]
Perpetual Debt And Equity Securities [Member]
Available For Sale Securities [Abstract]
Amortized Cost	13		22
Gross Unrealized Gains	1		1
Gross unrealized losses	0		0
Total Available-For-Sale, Fair Value	14		23
Other-Than-Temporary Impairments	0	[1]	0	[1]
Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Amortized Cost	5,256		4,883
Gross Unrealized Gains	119		238
Gross unrealized losses	(195)		(128)
Total Available-For-Sale, Fair Value	5,180		4,993
Other-Than-Temporary Impairments	(18)	[1]	(20)	[1]
Fixed Maturities [Member] | Variable Interest Entity Primary Beneficiary [Member]
Held To Maturity Securities [Abstract]
Total Held-To-Maturity, Fair Value	2,690
Fixed Maturities [Member] | U S Treasury And Government [Member]
Available For Sale Securities [Abstract]
Amortized Cost	1,203		819
Gross Unrealized Gains	23		40
Gross unrealized losses	(8)		(1)
Total Available-For-Sale, Fair Value	1,218		858
Other-Than-Temporary Impairments	0	[1]	0	[1]
Fixed Maturities [Member] | State And Municipal Bonds [Member]
Available For Sale Securities [Abstract]
Amortized Cost	1,463		1,446
Gross Unrealized Gains	35		97
Gross unrealized losses	(43)		(12)
Total Available-For-Sale, Fair Value	1,455		1,531
Other-Than-Temporary Impairments	0	[1]	0	[1]
Fixed Maturities [Member] | Foreign Governments [Member]
Available For Sale Securities [Abstract]
Amortized Cost	178		183
Gross Unrealized Gains	9		13
Gross unrealized losses	0		0
Total Available-For-Sale, Fair Value	187		196
Other-Than-Temporary Impairments	0	[1]	0	[1]
Fixed Maturities [Member] | Corporate Obligations [Member]
Available For Sale Securities [Abstract]
Amortized Cost	1,055		1,058
Gross Unrealized Gains	27		54
Gross unrealized losses	(38)		(20)
Total Available-For-Sale, Fair Value	1,044		1,092
Other-Than-Temporary Impairments	0	[1]	5	[1]
Fixed Maturities [Member] | Residential Mortgage-Backed Agency [Member]
Available For Sale Securities [Abstract]
Amortized Cost	892		939
Gross Unrealized Gains	11		19
Gross unrealized losses	(21)		(1)
Total Available-For-Sale, Fair Value	882		957
Other-Than-Temporary Impairments	0	[1]	0	[1]
Fixed Maturities [Member] | Residential Mortgage-Backed Non-Agency [Member]
Available For Sale Securities [Abstract]
Amortized Cost	71		86
Gross Unrealized Gains	11		11
Gross unrealized losses	(6)		(8)
Total Available-For-Sale, Fair Value	76		89
Other-Than-Temporary Impairments	0	[1]	0	[1]
Fixed Maturities [Member] | Commercial Mortgage-Backed [Member]
Available For Sale Securities [Abstract]
Amortized Cost	34		46
Gross Unrealized Gains	0		0
Gross unrealized losses	(1)		(4)
Total Available-For-Sale, Fair Value	33		42
Other-Than-Temporary Impairments	0	[1]	0	[1]
Fixed Maturities [Member] | Collateralized Debt Obligations [Member]
Available For Sale Securities [Abstract]
Amortized Cost	215		161
Gross Unrealized Gains	1		1
Gross unrealized losses	(66)		(71)
Total Available-For-Sale, Fair Value	150		91
Other-Than-Temporary Impairments	(18)	[1]	(25)	[1]
Fixed Maturities [Member] | Other Asset-Backed [Member]
Available For Sale Securities [Abstract]
Amortized Cost	145		145
Gross Unrealized Gains	2		3
Gross unrealized losses	(12)		(11)
Total Available-For-Sale, Fair Value	135		137
Other-Than-Temporary Impairments	$ 0	[1]	$ 0	[1]
[1] Represents unrealized gains or losses on other than temporarily impaired securities recognized in AOCI, which includes the non-credit component of impairments, as well as all subsequent changes in fair value of such impaired securities reported in AOCI.

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- Definition

Unrealized gains or losses on other-than-temporarily impaired securities recognized in AOCI, which includes the non-credit component of impairments, as well as all subsequent changes in fair value of such impaired securities reported in AOCI.

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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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- 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.

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Carrying amount of debt securities accounted for as held-to-maturity, net of adjustments including, but not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized, and fair value hedge accounting adjustments.

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As of the balance sheet date, the excess of fair value over carrying value (amortized cost) of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding gain.

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As of the balance sheet date, the excess of carrying value (amortized cost) over fair value of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding loss.

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