Fair Value Measurements (Financial Instruments Measured At Fair Value Using Significant Unobservable Inputs) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Jun. 30, 2013		Dec. 31, 2012		Jun. 30, 2012		Dec. 31, 2011
Equity Securities [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	$ 0		$ 2		$ 7		$ 2
Balance- Beginning of Period, Assets	4		12		3		13
Transfers out of Level 3, Assets	0		(10)		(1)		(10)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	0		(1)		(5)		0
Net Realized Gains/Losses, Assets			0		4		0
Purchases, Assets	0		1		1		4
Sales, Assets	0		0		(5)		(5)
Settlements, Assets			0				0
Balance-End of Period, Assets	4		4		4		4
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets			0				0
Short-term Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	1				8
Balance- Beginning of Period, Assets	9
Transfers out of Level 3, Assets	(2)				(2)
Purchases, Assets	0				2
Balance-End of Period, Assets	8				8
Other Long-term Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0		53		0		53
Balance- Beginning of Period, Assets	2,349		2,047		2,252		1,877
Transfers out of Level 3, Assets			0				0
Change in Net Unrealized Gains (Losses) included in OCI, Assets	(1)		13		34		37
Net Realized Gains/Losses, Assets	0		0		(2)		(7)
Purchases, Assets	138		121		387		366
Sales, Assets	(1)		(5)		(10)		(6)
Settlements, Assets	(96)		(51)		(272)		(142)
Balance-End of Period, Assets	2,389		2,178		2,389		2,178
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	0		0		(2)		(7)
Other Derivative Instruments [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3			0				0
Balance- Beginning of Period, Assets			1				3
Transfers out of Level 3, Assets			0				0
Change in Net Unrealized Gains (Losses) included in OCI, Assets			0				0
Net Realized Gains/Losses, Assets			0				(4)
Purchases, Assets			0				3
Sales, Assets			0				0
Settlements, Assets			(1)				(2)
Balance-End of Period, Assets			0				0
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets			0				0
Available-for-sale Securities [Member] | US Treasury and Government [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3			0				0
Balance- Beginning of Period, Assets			4				5
Transfers out of Level 3, Assets			(4)				(4)
Change in Net Unrealized Gains (Losses) included in OCI, Assets			0				0
Net Realized Gains/Losses, Assets			0				0
Purchases, Assets			0				0
Sales, Assets			0				0
Settlements, Assets			0				(1)
Balance-End of Period, Assets			0				0
Available-for-sale Securities [Member] | Foreign [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	1		5		33		6
Balance- Beginning of Period, Assets	48		20		60		33
Transfers out of Level 3, Assets	(8)		(6)		(49)		(7)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	2		0		(2)		0
Net Realized Gains/Losses, Assets	0		0		1		0
Purchases, Assets	12		6		15		46
Sales, Assets	(13)		0		(15)		(52)
Settlements, Assets	0		0		(1)		(1)
Balance-End of Period, Assets	42		25		42		25
Available-for-sale Securities [Member] | Corporate Debt Securities [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	12		5		29		33
Balance- Beginning of Period, Assets	114		137		102		134
Transfers out of Level 3, Assets	(1)		(26)		(30)		(35)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	(1)		3		(1)		6
Net Realized Gains/Losses, Assets	(1)		0		(2)		(1)
Purchases, Assets	6		11		39		19
Sales, Assets	(4)		0		(4)		(15)
Settlements, Assets	(4)		0		(12)		(11)
Balance-End of Period, Assets	121		130		121		130
Available-for-sale Securities [Member] | Mortgage Backed-Securities [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0		10		0		22
Balance- Beginning of Period, Assets	9		27		13		28
Transfers out of Level 3, Assets	0		0		0		(15)
Change in Net Unrealized Gains (Losses) included in OCI, Assets			0				0
Net Realized Gains/Losses, Assets			0				0
Purchases, Assets	0		0		0		4
Sales, Assets	0		(7)		(3)		(7)
Settlements, Assets	0		(1)		(1)		(3)
Balance-End of Period, Assets	9		29		9		29
Available-for-sale Securities [Member] | States, Municipalities, And Political Subdivisions [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3			0				1
Balance- Beginning of Period, Assets			1				1
Transfers out of Level 3, Assets			0				0
Change in Net Unrealized Gains (Losses) included in OCI, Assets			0				0
Net Realized Gains/Losses, Assets			0				0
Purchases, Assets			0				0
Sales, Assets			0				0
Settlements, Assets			0				(1)
Balance-End of Period, Assets			1				1
Guaranteed Minimum Income Benefit [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	514	[1]	1,279	[1]	514	[1]	1,279	[1]	652	[1]	1,119	[1]	1,354	[1]	1,319	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	(138)	[1]	(75)	[1]	(605)	[1]	(40)	[1]
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities	(138)		(75)		(605)		(40)
Reported liabilities	$ 746		$ 1,500		$ 746		$ 1,500				$ 1,400		$ 1,600		$ 1,500

[1] Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value. Excluded from the table above is the portion of the GLB derivative liability classified as Future policy benefits in the consolidated balance sheets. Refer to Note 5 for additional information.