Investments (Details 12) (USD $) In Millions, unless otherwise specified																									12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Office buildings	Dec. 31, 2011 Office buildings	Dec. 31, 2012 Retail	Dec. 31, 2011 Retail	Dec. 31, 2012 Apartment complex	Dec. 31, 2011 Apartment complex	Dec. 31, 2012 Warehouse	Dec. 31, 2011 Warehouse	Dec. 31, 2012 Other;	Dec. 31, 2011 Other;	Dec. 31, 2012 California	Dec. 31, 2011 California	Dec. 31, 2012 Illinois	Dec. 31, 2011 Illinois	Dec. 31, 2012 New York	Dec. 31, 2011 New York	Dec. 31, 2012 Texas	Dec. 31, 2011 Texas	Dec. 31, 2012 New Jersey	Dec. 31, 2011 New Jersey	Dec. 31, 2012 Pennsylvania	Dec. 31, 2011 Pennsylvania	Dec. 31, 2012 Mortgage loans, not in foreclosure loan	Dec. 31, 2012 Mortgage loans, not in foreclosure 2013 loan	Dec. 31, 2012 Mortgage loans, not in foreclosure 2014 loan	Dec. 31, 2012 Mortgage loans, not in foreclosure 2015 loan	Dec. 31, 2012 Mortgage loans, not in foreclosure 2016 loan	Dec. 31, 2012 Mortgage loans, not in foreclosure Thereafter loan
Investments
Threshold percentage of mortgage loans to total carrying value	5.00%
Mortgage Loans on Real Estate
Percentage of mortgage portfolio carrying value	100.00%	100.00%	26.60%	27.90%	22.70%	24.80%	20.60%	19.60%	19.70%	19.40%	10.40%	8.30%	23.60%	22.60%	8.10%	9.10%	6.40%	5.80%	6.40%	6.20%	6.20%	6.50%	4.90%	5.30%	100.00%	5.20%	11.50%	14.70%	12.40%	56.20%
Number of mortgage loans																									579	42	64	67	72	334
Mortgage loans	$ 6,570	$ 7,139																							$ 6,566	$ 339	$ 758	$ 968	$ 813	$ 3,688
Mortgage loans in the process of foreclosure											$ 4