Fair Value Measurements (Financial Instruments Measured At Fair Value Using Significant Unobservable Inputs) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012		Mar. 31, 2013		Dec. 31, 2012		Mar. 31, 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	$ 7		$ 0		$ 7		$ 0
Balance- Beginning of Period, Assets	2		10		3		13
Transfers out of Level 3, Assets	0		0		(1)		0
Change in Net Unrealized Gains (Losses) included in OCI, Assets	(5)		0		(5)		1
Net Realized Gains/Losses, Assets			0				0
Purchases, Assets	1		2		1		3
Sales, Assets	(5)		0		(5)		(5)
Settlements, Assets			0				0
Balance-End of Period, Assets	4		12		4		12
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	7				7
Purchases, Assets	2				2
Balance-End of Period, Assets	9				9
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		0		0		0
Balance- Beginning of Period, Assets	2,328		1,954		2,252		1,877
Transfers out of Level 3, Assets			0				0
Change in Net Unrealized Gains (Losses) included in OCI, Assets	13		16		35		24
Net Realized Gains/Losses, Assets	(1)		(5)		(2)		(7)
Purchases, Assets	113		132		249		245
Sales, Assets	0		0		(9)		(1)
Settlements, Assets	(104)		(50)		(176)		(91)
Balance-End of Period, Assets	2,349		2,047		2,349		2,047
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	(1)		(5)		(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			(1)				(4)
Purchases, Assets			3				3
Sales, Assets			0				0
Settlements, Assets			0				(1)
Balance-End of Period, Assets			1				1
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets			0				(1)
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			5				0
Balance- Beginning of Period, Assets			0				5
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			(1)				(1)
Balance-End of Period, Assets			4				4
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	29		1		32		1
Balance- Beginning of Period, Assets	35		49		60		33
Transfers out of Level 3, Assets	(14)		0		(41)		(1)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	(4)		0		(4)		0
Net Realized Gains/Losses, Assets	0		0		1		0
Purchases, Assets	3		6		3		40
Sales, Assets	(1)		(35)		(2)		(52)
Settlements, Assets	0		(1)		(1)		(1)
Balance-End of Period, Assets	48		20		48		20
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	5		28		17		28
Balance- Beginning of Period, Assets	118		117		102		134
Transfers out of Level 3, Assets	(27)		(2)		(29)		(9)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	(1)		1		0		3
Net Realized Gains/Losses, Assets	(1)		(1)		(1)		(1)
Purchases, Assets	23		5		33		8
Sales, Assets	0		(7)		0		(15)
Settlements, Assets	(3)		(4)		(8)		(11)
Balance-End of Period, Assets	114		137		114		137
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		12		0		12
Balance- Beginning of Period, Assets	13		19		13		28
Transfers out of Level 3, Assets	0		(3)		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	(3)		0		(3)		0
Settlements, Assets	(1)		(1)		(1)		(2)
Balance-End of Period, Assets	9		27		9		27
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			1				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			(1)				(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	652	[1]	1,354	[1]	652	[1]	1,354	[1]	753	[1]	1,119	[1]	863	[1]	1,319	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	(101)	[1]	491	[1]	(467)	[1]	35	[1]
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities	(101)		491		(467)		35
Reported liabilities	$ 880		$ 1,600		$ 880		$ 1,600				$ 1,400		$ 1,050		$ 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.