Fair Value Measurements (Financial Instruments Measured At Fair Value Using Significant Unobservable Inputs) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011		Dec. 31, 2011	Dec. 31, 2010
Equity Securities [Member]
Fair Value Measurements [Line Items]
Balance-Beginning of Period, Assets	$ 13		$ 13
Changes in Net Unrealized Gains (Losses) included in OCI, Assets	1		(1)
Net Realized Gains/Losses, Assets			2
Purchases, Assets	1
Sales, Assets	(5)		(4)
Balance-End of Period, Assets	10		10
Other Investments [Member]
Fair Value Measurements [Line Items]
Balance-Beginning of Period, Assets	1,877		1,432
Changes in Net Unrealized Gains (Losses) included in OCI, Assets	9		42
Net Realized Gains/Losses, Assets	(2)
Purchases, Assets	113		90
Sales, Assets	(2)
Settlements, Assets	(41)
Balance-End of Period, Assets	1,954		1,564
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	(2)
Other Derivative Instruments [Member]
Fair Value Measurements [Line Items]
Balance-Beginning of Period, Assets	3		4
Net Realized Gains/Losses, Assets	(3)		1
Settlements, Assets	(1)		(1)
Balance-End of Period, Assets	(1)		4
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	(3)		1
Guaranteed Living Benefits [Member]
Fair Value Measurements [Line Items]
Guaranteed minimum benefits fair value derivative adjustment in liability	863		449		1,300	507
Balance-Beginning of period, Liabilities	1,319	[1]	507	[2]
Net Realized Gains/Losses, Liabilities	(456)	[1]	(58)	[2]
Balance-End of Period, Liabilities	863	[1]	449	[2]
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities	(456)	[1]	(58)	[2]
Reported liabilities	1,050		596		1,500	648
Available-For-Sale Debt Securities [Member] | U.S. Treasury And Agency [Member]
Fair Value Measurements [Line Items]
Balance-Beginning of Period, Assets	5
Transfers out of Level 3, Assets	(5)
Available-For-Sale Debt Securities [Member] | Foreign [Member]
Fair Value Measurements [Line Items]
Balance-Beginning of Period, Assets	33		26
Transfers into Level 3, Assets			4
Transfers out of Level 3, Assets	(1)		(1)
Changes in Net Unrealized Gains (Losses) included in OCI, Assets			(1)
Purchases, Assets	34
Sales, Assets	(17)		(1)
Settlements, Assets			(1)
Balance-End of Period, Assets	49		26
Available-For-Sale Debt Securities [Member] | Corporate Securities [Member]
Fair Value Measurements [Line Items]
Balance-Beginning of Period, Assets	134		115
Transfers into Level 3, Assets			5
Transfers out of Level 3, Assets	(7)		(4)
Changes in Net Unrealized Gains (Losses) included in OCI, Assets	2		1
Net Realized Gains/Losses, Assets			(1)
Purchases, Assets	3		19
Sales, Assets	(8)		(19)
Settlements, Assets	(7)		(3)
Balance-End of Period, Assets	117		113
Available-For-Sale Debt Securities [Member] | Mortgage-Backed Securities [Member]
Fair Value Measurements [Line Items]
Balance-Beginning of Period, Assets	28		39
Transfers into Level 3, Assets			1
Transfers out of Level 3, Assets	(12)
Purchases, Assets	4		46
Sales, Assets			(3)
Settlements, Assets	(1)		(2)
Balance-End of Period, Assets	19		81
Available-For-Sale Debt Securities [Member] | States, Municipalities, And Political Subdivisions [Member]
Fair Value Measurements [Line Items]
Balance-Beginning of Period, Assets			2		1
Settlements, Assets			(1)
Balance-End of Period, Assets	$ 1		$ 1		$ 1

[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 $596 million at March 31, 2011, and $648 million at December 31, 2010, which includes a fair value derivative adjustment of $449 million and $507 million, respectively.