Supplemental Cash Flow Information (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Supplemental Cash Flow Information
Non-cash modifications of certain mortgage loans, fixed income securities, limited partnerships and other investments, as well as mergers completed with equity securities	$ 138	$ 450
Net change in proceeds managed
Net change in short-term investments	(240)	(84)
Operating cash flow used	(240)	(84)
Net change in liabilities
Liabilities for collateral, beginning of year	(263)	(465)
Liabilities for collateral, end of period	(503)	(549)
Operating cash flow provided	$ 240	$ 84