Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Reclassification of loss adjustment expense			$ 53	$ 49
Pretax benefit resulted from an adjustment to valuation of reserves, net of DAC and DSIC amortization	41
DSIC amortization expense	11
Decrease to tax expense resulting from out-of-period correction for deferred tax balance	16
Increase to tax expense resulting from out-of-period correction for tax item related to securities lending activities		$ 32