Fair Value Measurements (Financial Instruments Measured At Fair Value Using Significant Unobservable Inputs) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012		Dec. 31, 2012	Dec. 31, 2011
Schedule Of Fair Value Measurements [Line Items]
Document Period End Date	Mar. 31, 2013
Equity Securities [Member]
Schedule Of Fair Value Measurements [Line Items]
Balance- Beginning of Period, Assets	$ 3		$ 13
Transfers into Level 3, Assets	0
Transfers out of Level 3, Assets	(1)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	0		1
Net Realized Gains/Losses, Assets			0
Purchases, Assets	0		1
Sales, Assets	0		(5)
Settlements, Assets			0
Balance-End of Period, Assets	2		10
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets			0
Other Long-term Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Balance- Beginning of Period, Assets	2,252		1,877
Transfers into Level 3, Assets	0
Change in Net Unrealized Gains (Losses) included in OCI, Assets	22		9
Net Realized Gains/Losses, Assets	(1)		(2)
Purchases, Assets	136		113
Sales, Assets	(9)		(2)
Settlements, Assets	(72)		(41)
Balance-End of Period, Assets	2,328		1,954
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	(1)		(2)
Other Derivative Instruments [Member]
Schedule Of Fair Value Measurements [Line Items]
Balance- Beginning of Period, Assets			3
Net Realized Gains/Losses, Assets			(3)
Settlements, Assets			(1)
Balance-End of Period, Assets			(1)	[1]
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets			(3)
Available-for-sale Securities [Member] | US Treasury and Government [Member]
Schedule Of Fair Value Measurements [Line Items]
Balance- Beginning of Period, Assets			5
Transfers out of Level 3, Assets			(5)
Net Realized Gains/Losses, Assets			0
Purchases, Assets			0
Balance-End of Period, Assets			0
Available-for-sale Securities [Member] | Foreign [Member]
Schedule Of Fair Value Measurements [Line Items]
Balance- Beginning of Period, Assets	60		33
Transfers into Level 3, Assets	3
Transfers out of Level 3, Assets	(27)		(1)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	0		0
Net Realized Gains/Losses, Assets	1
Purchases, Assets	0		34
Sales, Assets	(1)		(17)
Settlements, Assets	(1)		0
Balance-End of Period, Assets	35		49
Available-for-sale Securities [Member] | Corporate Debt Securities [Member]
Schedule Of Fair Value Measurements [Line Items]
Balance- Beginning of Period, Assets	102		134
Transfers into Level 3, Assets	12
Transfers out of Level 3, Assets	(2)		(7)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	1		2
Net Realized Gains/Losses, Assets	0
Purchases, Assets	10		3
Sales, Assets	0		(8)
Settlements, Assets	(5)		(7)
Balance-End of Period, Assets	118		117
Available-for-sale Securities [Member] | Mortgage Backed-Securities [Member]
Schedule Of Fair Value Measurements [Line Items]
Balance- Beginning of Period, Assets	13		28
Transfers into Level 3, Assets	0
Transfers out of Level 3, Assets	0		(12)
Purchases, Assets	0		4
Sales, Assets	0
Settlements, Assets	0		(1)
Balance-End of Period, Assets	13		19
Available-for-sale Securities [Member] | States, Municipalities, And Political Subdivisions [Member]
Schedule Of Fair Value Measurements [Line Items]
Balance- Beginning of Period, Assets						1
Balance-End of Period, Assets			1			1
Guaranteed Minimum Income Benefit [Member]
Schedule Of Fair Value Measurements [Line Items]
Balance- Beginning of Period, Liabilities	1,119	[2]	1,319
Net Realized Gains/Losses, Liabilities	(366)	[2]	(456)
Balance- End of Period, Liabilities	753	[2]	863
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities	(366)		(456)
Reported liabilities	$ 1,000		$ 1,050		$ 1,400	$ 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. The liability for GLB reinsurance was $1.05 billion at March 31, 2012, and $1.5 billion at December 31, 2011, which includes a fair value derivative adjustment of $863 million and $1.3 billion, respectively.

[2] 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.