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			3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended						3 Months Ended				9 Months Ended
	Sep. 30, 2012 Equity Securities [Member]	Sep. 30, 2012 Equity Securities [Member]	Sep. 30, 2011 Equity Securities [Member]	Jun. 30, 2011 Equity Securities [Member]	Sep. 30, 2012 Other Long-term Investments [Member]	Sep. 30, 2011 Other Long-term Investments [Member]	Sep. 30, 2012 Other Long-term Investments [Member]	Sep. 30, 2011 Other Long-term Investments [Member]	Sep. 30, 2012 Other Derivative Instruments [Member]	Sep. 30, 2011 Other Derivative Instruments [Member]	Sep. 30, 2012 Other Derivative Instruments [Member]	Sep. 30, 2011 Other Derivative Instruments [Member]	Sep. 30, 2012 Available-for-sale Securities [Member] US Treasury and Government [Member]	Sep. 30, 2012 Available-for-sale Securities [Member] US Treasury and Government [Member]	Sep. 30, 2012 Available-for-sale Securities [Member] Foreign [Member]	Sep. 30, 2011 Available-for-sale Securities [Member] Foreign [Member]	Sep. 30, 2012 Available-for-sale Securities [Member] Foreign [Member]	Sep. 30, 2011 Available-for-sale Securities [Member] Foreign [Member]	Sep. 30, 2012 Available-for-sale Securities [Member] Corporate Debt Securities [Member]	Sep. 30, 2011 Available-for-sale Securities [Member] Corporate Debt Securities [Member]	Sep. 30, 2012 Available-for-sale Securities [Member] Corporate Debt Securities [Member]	Sep. 30, 2011 Available-for-sale Securities [Member] Corporate Debt Securities [Member]	Sep. 30, 2012 Available-for-sale Securities [Member] Mortgage Backed-Securities [Member]	Sep. 30, 2011 Available-for-sale Securities [Member] Mortgage Backed-Securities [Member]	Sep. 30, 2012 Available-for-sale Securities [Member] Mortgage Backed-Securities [Member]	Sep. 30, 2011 Available-for-sale Securities [Member] Mortgage Backed-Securities [Member]	Sep. 30, 2012 Available-for-sale Securities [Member] States, Municipalities, And Political Subdivisions [Member]	Sep. 30, 2011 Available-for-sale Securities [Member] States, Municipalities, And Political Subdivisions [Member]	Jun. 30, 2012 Available-for-sale Securities [Member] States, Municipalities, And Political Subdivisions [Member]	Jun. 30, 2011 Available-for-sale Securities [Member] States, Municipalities, And Political Subdivisions [Member]	Sep. 30, 2012 Guaranteed Minimum Income Benefit [Member]		Sep. 30, 2011 Guaranteed Minimum Income Benefit [Member]		Sep. 30, 2012 Guaranteed Minimum Income Benefit [Member]		Sep. 30, 2011 Guaranteed Minimum Income Benefit [Member]		Dec. 31, 2011 Guaranteed Minimum Income Benefit [Member]	Jun. 30, 2011 Guaranteed Minimum Income Benefit [Member]	Dec. 31, 2010 Guaranteed Minimum Income Benefit [Member]
Schedule Of Fair Value Measurements [Line Items]
Balance- Beginning of Period, Assets	$ 12	$ 13	$ 13	$ 10	$ 2,047	$ 1,680	$ 1,877	$ 1,432	$ 1	$ 4	$ 3	$ 4	$ 4	$ 5	$ 20	$ 27	$ 33	$ 26	$ 137	$ 142	$ 134	$ 115	$ 27	$ 34	$ 28	$ 39	$ 1	$ 2	$ 1	$ 1
Balance- Beginning of Period, Liabilities																															1,354	[1]	524	[2]	1,319	[1]	507
Transfers into Level 3, Assets	2	2			53		53								5		6	9	5		33	34	10		22	4	1
Transfers out of Level 3, Assets	(10)	(10)											(4)	(4)	(6)	(11)	7	(18)	(26)		(35)	(4)		(13)	(15)	(48)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	(1)		1		13	(59)	37	(110)										1	3	6	6	5
Net Realized Gains/Losses, Assets			4			(1)	(7)	(4)		5	(4)	6				(1)					(1)	(2)
Net Realized Gains/Losses, Liabilities																															(75)	[1]	952	[2]	(40)	[1]	969	[3]
Purchases, Assets	1	4	2		121	85	366	418			3				6	1	46	6	11	1	19	23			4	46
Sales, Assets		(5)	(8)		(5)		(6)	(55)									(52)	(3)		(3)	(15)	(23)	(7)	(2)	(7)	(17)
Settlements, Assets					(51)	(58)	(142)	(136)	(1)	(1)	(2)	(2)		(1)			(1)	(3)		(9)	(11)	(13)	(1)	(1)	(3)	(6)	(1)	(1)							0
Balance-End of Period, Assets	4	4	10	10	2,178	1,765	2,178	1,765	0	8	0	8	0	0	25	16	25	16	130	125	130	125	29	18	29	18	1	1	1	1
Balance- End of Period, Liabilities																															1,279	[1]	1,476	[2]	1,279	[1]	1,476	[2]
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets						(1)	(7)	(4)		4		4
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities																															(75)		952	[2]	(40)	[1]	969	[3]
Reported liabilities																															$ 1,500		$ 1,635		$ 1,500		$ 1,635		$ 1,500	$ 676	$ 648

[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.

[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. The liability for GLB reinsurance was $1,635 million at September 30, 2011, and $676 million at June 30, 2011, which includes a fair value derivative adjustment of $1,476 million and $524 million, respectively.

[3] 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 $1,635 million at September 30, 2011, and $648 million at December 31, 2010, which includes a fair value derivative adjustment of $1,476 million and $507 million, respectively.