Investments (Details 13) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) loan	Dec. 31, 2015 USD ($)
Investments [Abstract]
Threshold percentage of mortgage loans to total carrying value	5.00%
Mortgage Loans on Real Estate
Carrying value	$ 4,486	$ 4,338
Percent	100.00%	100.00%
Apartment complex
Mortgage Loans on Real Estate
Percent	27.60%	26.40%
Office buildings
Mortgage Loans on Real Estate
Percent	23.90%	22.70%
Retail
Mortgage Loans on Real Estate
Percent	20.40%	21.30%
Warehouse
Mortgage Loans on Real Estate
Percent	17.00%	18.40%
Other
Mortgage Loans on Real Estate
Percent	11.10%	11.20%
California
Mortgage Loans on Real Estate
Percent	19.30%	21.30%
Texas
Mortgage Loans on Real Estate
Percent	10.50%	9.70%
New Jersey
Mortgage Loans on Real Estate
Percent	8.20%	8.70%
Illinois
Mortgage Loans on Real Estate
Percent	6.70%	7.10%
Florida
Mortgage Loans on Real Estate
Percent	5.40%	5.30%
Mortgage loans, not in foreclosure
Mortgage Loans on Real Estate
Number of loans | loan	303
Carrying value	$ 4,486
Percent	100.00%
Mortgage loans, not in foreclosure | 2017
Mortgage Loans on Real Estate
Number of loans | loan	28
Carrying value	$ 295
Percent	6.60%
Mortgage loans, not in foreclosure | 2018
Mortgage Loans on Real Estate
Number of loans | loan	29
Carrying value	$ 336
Percent	7.50%
Mortgage loans, not in foreclosure | 2019
Mortgage Loans on Real Estate
Number of loans | loan	10
Carrying value	$ 267
Percent	6.00%
Mortgage loans, not in foreclosure | 2020
Mortgage Loans on Real Estate
Number of loans | loan	14
Carrying value	$ 190
Percent	4.20%
Mortgage loans, not in foreclosure | Thereafter
Mortgage Loans on Real Estate
Number of loans | loan	222
Carrying value	$ 3,398
Percent	75.70%