Insurance In Force (Summary Of Components Of Financial Guarantee Net Premiums Earned, Including Premiums Assumed From And Ceded To Other Companies) (Details) (Non Variable Interest Entities [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Non Variable Interest Entities [Member]
Direct	$ 505	$ 516	$ 726
Assumed	112	106	107
Gross	617	622	833
Ceded	(12)	(28)	(87)
Premiums earned (net of ceded premiums of $12, $28, and $87)	$ 605	$ 594	$ 746