Investments (Details 33) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	$ 41,035	$ 40,440
% of Total	100.00%	100.00%
Estimated Fair Value	42,978	42,105
% of Total	100.00%	100.00%
Less than 65% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	29,084	25,995
% of Total	70.90%	64.30%
Estimated Fair Value	30,840	27,581
% of Total	71.80%	65.50%
65% to 75% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	7,816	8,997
% of Total	19.00%	22.30%
Estimated Fair Value	8,132	9,387
% of Total	18.90%	22.30%
76% to 80% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	1,156	1,474
% of Total	2.80%	3.60%
Estimated Fair Value	1,182	1,473
% of Total	2.70%	3.50%
Greater than 80% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	2,979	3,974
% of Total	7.30%	9.80%
Estimated Fair Value	2,824	3,664
% of Total	6.60%	8.70%
Greater than 1.20x [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	38,004	37,122
Greater than 1.20x [Member] | Less than 65% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	28,022	24,983
Greater than 1.20x [Member] | 65% to 75% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	7,218	8,275
Greater than 1.20x [Member] | 76% to 80% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	831	1,150
Greater than 1.20x [Member] | Greater than 80% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	1,933	2,714
1.00x - 1.20x [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	1,818	1,762
1.00x - 1.20x [Member] | Less than 65% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	607	448
1.00x - 1.20x [Member] | 65% to 75% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	398	336
1.00x - 1.20x [Member] | 76% to 80% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	96	98
1.00x - 1.20x [Member] | Greater than 80% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	717	880
Less than 1.00x [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	1,213	1,556
Less than 1.00x [Member] | Less than 65% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	455	564
Less than 1.00x [Member] | 65% to 75% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	200	386
Less than 1.00x [Member] | 76% to 80% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	229	226
Less than 1.00x [Member] | Greater than 80% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	$ 329	$ 380