Investments (Details 13) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) loan	Dec. 31, 2014 USD ($)
Investments [Abstract]
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%
Carrying value	$ 4,338	$ 4,188
Apartment complex
Mortgage Loans on Real Estate
Percentage of mortgage portfolio carrying value	26.40%	23.30%
Office buildings
Mortgage Loans on Real Estate
Percentage of mortgage portfolio carrying value	22.70%	24.30%
Retail
Mortgage Loans on Real Estate
Percentage of mortgage portfolio carrying value	21.30%	22.20%
Warehouse
Mortgage Loans on Real Estate
Percentage of mortgage portfolio carrying value	18.40%	17.80%
Other
Mortgage Loans on Real Estate
Percentage of mortgage portfolio carrying value	11.20%	12.40%
California
Mortgage Loans on Real Estate
Percentage of mortgage portfolio carrying value	21.30%	23.90%
Texas
Mortgage Loans on Real Estate
Percentage of mortgage portfolio carrying value	9.70%	8.00%
New Jersey
Mortgage Loans on Real Estate
Percentage of mortgage portfolio carrying value	8.70%	8.00%
Illinois
Mortgage Loans on Real Estate
Percentage of mortgage portfolio carrying value	7.10%	9.40%
Florida
Mortgage Loans on Real Estate
Percentage of mortgage portfolio carrying value	5.30%	5.00%
New York
Mortgage Loans on Real Estate
Percentage of mortgage portfolio carrying value	4.40%	5.90%
Mortgage loans, not in foreclosure
Mortgage Loans on Real Estate
Percentage of mortgage portfolio carrying value	100.00%
Number of loans | loan	317
Carrying value	$ 4,338
Mortgage loans, not in foreclosure | 2016
Mortgage Loans on Real Estate
Percentage of mortgage portfolio carrying value	6.70%
Number of loans | loan	31
Carrying value	$ 289
Mortgage loans, not in foreclosure | 2017
Mortgage Loans on Real Estate
Percentage of mortgage portfolio carrying value	8.70%
Number of loans | loan	34
Carrying value	$ 379
Mortgage loans, not in foreclosure | 2018
Mortgage Loans on Real Estate
Percentage of mortgage portfolio carrying value	9.00%
Number of loans | loan	33
Carrying value	$ 392
Mortgage loans, not in foreclosure | 2019
Mortgage Loans on Real Estate
Percentage of mortgage portfolio carrying value	5.40%
Number of loans | loan	9
Carrying value	$ 234
Mortgage loans, not in foreclosure | Thereafter
Mortgage Loans on Real Estate
Percentage of mortgage portfolio carrying value	70.20%
Number of loans | loan	210
Carrying value	$ 3,044