Related Party (Affiliated Asset Transfers) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Related Party Transactions [Line Items]
Fixed maturity asset transfer amortized cost	$ 91	$ 123	$ 27
Fixed maturity asset transfer fair value	103	141	28
Realized gain on fixed maturity asset transfer	8	11	1
Commercial mortgage loans asset transfer amortized cost			27
Commercial mortgage loans asset transfer fair value			28
Realized gain on commerical mortgage loan asset transfer			$ 1