Assumed Life Reinsurance Programs Involving Minimum Benefit Guarantees Under Annuity Contracts (Narrative) (Details) (USD $) In Millions, unless otherwise specified					3 Months Ended
	Mar. 31, 2012 Guaranteed Minimum Death Benefits [Member]	Dec. 31, 2011 Guaranteed Minimum Death Benefits [Member]	Mar. 31, 2012 Guaranteed Living Benefits [Member]	Mar. 31, 2011 Guaranteed Living Benefits [Member]	Mar. 31, 2012 Guaranteed Minimum Deaths Benefits And Guaranteed Living Benefits [Member]	Dec. 31, 2011 Guaranteed Minimum Deaths Benefits And Guaranteed Living Benefits [Member]	Mar. 31, 2012 Guaranteed Living Benefits [Member]	Dec. 31, 2011 Guaranteed Living Benefits [Member]	Mar. 31, 2011 Guaranteed Living Benefits [Member]	Dec. 31, 2010 Guaranteed Living Benefits [Member]
Guaranteed Minimum Benefits [Line Items]
Reported liabilities	$ 127	$ 138					$ 1,050	$ 1,500	$ 596	$ 648
Fair value derivative adjustment in liability							863	1,300	449	507
Net amount at risk	1,500	1,800	221	380
Discounting assumption used in the calculation of the benefit reserve averaging - lower range	1.00%		3.00%		1.00%		3.00%
Discounting assumption used in the calculation of the benefit reserve averaging - upper range	2.00%		4.00%		2.00%		4.00%
Percent of Annuity 2000 mortality table used for mortality assumption	100.00%				100.00%
Mortality according to percent of the Annuity 2000 mortality table	100.00%
Total claim amount payable, if all of the Company's cedants' policyholders covered were to die immediately	500				800
Average attained age of all policyholders under all benefits reinsured, years					67
GMBD net amount of risk					136	182
GLB net amount of risk					$ 660	$ 998