Investments (Mortgage Loans by Portfolio Segment) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Company-held mortgage loans held-for-investment, net
Commercial mortgage loans	$ 45,445	$ 44,012
Percentage of loans receivable on commercial mortgage loans	66.20%	65.60%
Agricultural mortgage loans	$ 13,226	$ 13,188
Percentage of loans receivable on agricultural mortgage loans	19.30%	19.60%
Residential mortgage loans	$ 9,800	$ 9,734
Percentage of loans receivable on residential mortgage loans	14.30%	14.50%
Subtotal	$ 68,471	$ 66,934
Percentage of loans receivable on subtotal	99.80%	99.70%
Valuation allowances	$ (381)	$ (318)	$ (315)	$ (305)
Percentage of loans receivable on valuation allowances	(0.60%)	(0.50%)
Subtotal mortgage loans, net	$ 68,090	$ 66,616
Percentage of loans receivable on subtotal mortgage loans held-for-investment, net	99.20%	99.20%
Percentage of residential mortgage loans - FVO	0.60%	0.50%
Percentage of loans receivable on commercial mortgage loans held by consolidated securitization entities - fair value option	0.20%	0.30%
Mortgage loans held-for-sale
Total mortgage loans, net	$ 68,651	$ 67,102
Percentage of loans held for sale on total mortgage loans, net	100.00%	100.00%
Residential — FVO
Mortgage loans held-for-sale
Total mortgage loans, net	$ 392	$ 314
Consolidated Securitization Entities
Mortgage loans held-for-sale
Total mortgage loans, net	$ 169	$ 172