Supplemental Cash Flow Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
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	$ 323	$ 601	$ 664
Non-cash financing activities related to the issuance of shares for vested restricted stock units	39	18	23
Liabilities for collateral received reported in other liabilities and accrued expenses	784	419	461
Obligations to return cash collateral for over-the-counter ("OTC") derivatives reported in other liabilities and accrued expenses or other investments	24	43	23
Net change in proceeds managed
Net change in short-term investments	(341)	21	171
Operating cash flow (used) provided	(341)	21	171
Net change in cash	(5)	1	3
Net change in proceeds managed	(346)	22	174
Net change in liabilities
Liabilities for collateral, beginning of year	(462)	(484)	(658)
Liabilities for collateral, end of period	(808)	(462)	(484)
Operating cash flow provided (used)	$ 346	$ (22)	$ (174)