Investments (Credit Quality of Commercial Mortgage Loans) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	$ 40,398	$ 40,926
% of Total	100.00%	100.00%
Estimated Fair Value	42,205	42,456
% of Total	100.00%	100.00%
Less than 65% [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	32,023	32,007
% of Total	79.30%	78.20%
Estimated Fair Value	33,790	33,519
% of Total	80.00%	78.90%
65% to 75% [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	6,462	6,947
% of Total	16.00%	17.00%
Estimated Fair Value	6,568	7,039
% of Total	15.60%	16.60%
76% to 80% [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	850	906
% of Total	2.10%	2.20%
Estimated Fair Value	847	892
% of Total	2.00%	2.10%
Greater than 80% [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	1,063	1,066
% of Total	2.60%	2.60%
Estimated Fair Value	1,000	1,006
% of Total	2.40%	2.40%
Greater than 1.20x [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	37,749	38,098
Greater than 1.20x [Member] | Less than 65% [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	30,719	30,552
Greater than 1.20x [Member] | 65% to 75% [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	5,815	6,360
Greater than 1.20x [Member] | 76% to 80% [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	555	525
Greater than 1.20x [Member] | Greater than 80% [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	660	661
1.00x - 1.20x [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	1,469	1,486
1.00x - 1.20x [Member] | Less than 65% [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	537	614
1.00x - 1.20x [Member] | 65% to 75% [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	498	438
1.00x - 1.20x [Member] | 76% to 80% [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	192	192
1.00x - 1.20x [Member] | Greater than 80% [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	242	242
Less than 1.00x [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	1,180	1,342
Less than 1.00x [Member] | Less than 65% [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	767	841
Less than 1.00x [Member] | 65% to 75% [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	149	149
Less than 1.00x [Member] | 76% to 80% [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	103	189
Less than 1.00x [Member] | Greater than 80% [Member]
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	$ 161	$ 163