Investments (Commercial Mortgage and Other Loans) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Servicing Assets at Fair Value [Line Items]
Total commercial mortgage and agricultural property loans by property type		$ 51,985	$ 49,046
Valuation Allowance		(98)	(99)
Total net commercial mortgage and agricultural property loans by property type		51,887	48,947
Loans and Leases Receivable, Gross, Consumer, Real Estate		900	1,625
Total net other loans		892	1,612
Commercial mortgage and other loans	[1]	$ 52,779	$ 50,559
% of Total		100.00%	100.00%
Allowance for Loan and Lease Losses, Real Estate		$ 8	$ 13
Total commercial mortgage loans
Servicing Assets at Fair Value [Line Items]
Total commercial mortgage and agricultural property loans by property type		$ 49,027	$ 46,187
% of Total		94.30%	94.20%
Uncollateralized loans
Servicing Assets at Fair Value [Line Items]
Loans and Leases Receivable, Gross, Consumer, Real Estate		$ 638	$ 1,012
Residential property loans
Servicing Assets at Fair Value [Line Items]
Loans and Leases Receivable, Gross, Consumer, Real Estate		252	301
Other collateralized loans
Servicing Assets at Fair Value [Line Items]
Loans and Leases Receivable, Gross, Consumer, Real Estate		10	312
Office
Servicing Assets at Fair Value [Line Items]
Total commercial mortgage and agricultural property loans by property type		$ 12,424	$ 11,226
% of Total		23.90%	22.90%
Retail
Servicing Assets at Fair Value [Line Items]
Total commercial mortgage and agricultural property loans by property type		$ 8,555	$ 8,917
% of Total		16.50%	18.20%
Apartments/Multi-Family
Servicing Assets at Fair Value [Line Items]
Total commercial mortgage and agricultural property loans by property type		$ 13,733	$ 12,034
% of Total		26.40%	24.50%
Industrial
Servicing Assets at Fair Value [Line Items]
Total commercial mortgage and agricultural property loans by property type		$ 8,075	$ 7,775
% of Total		15.50%	15.90%
Hospitality
Servicing Assets at Fair Value [Line Items]
Total commercial mortgage and agricultural property loans by property type		$ 2,274	$ 2,513
% of Total		4.40%	5.10%
Other
Servicing Assets at Fair Value [Line Items]
Total commercial mortgage and agricultural property loans by property type		$ 3,966	$ 3,722
% of Total		7.60%	7.60%
Agricultural property loans
Servicing Assets at Fair Value [Line Items]
Total commercial mortgage and agricultural property loans by property type		$ 2,958	$ 2,859
% of Total		5.70%	5.80%

[1] See Note 5 for details of balances associated with variable interest entities.