Investments (Details 33) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	$ 40,329	$ 40,440
% of Total	100.00%	100.00%
Estimated Fair Value	42,021	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	27,295	25,995
% of Total	67.70%	64.30%
Estimated Fair Value	29,059	27,581
% of Total	69.20%	65.50%
65% to 75% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	7,968	8,997
% of Total	19.80%	22.30%
Estimated Fair Value	8,354	9,387
% of Total	19.90%	22.30%
76% to 80% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	1,373	1,474
% of Total	3.40%	3.60%
Estimated Fair Value	1,197	1,473
% of Total	2.80%	3.50%
Greater than 80% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	3,693	3,974
% of Total	9.10%	9.80%
Estimated Fair Value	3,411	3,664
% of Total	8.10%	8.70%
Greater than 1.20x [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	37,175	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	26,167	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	7,456	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	1,036	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	2,516	2,714
1.00x - 1.20x [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	1,673	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	590	448
1.00x - 1.20x [Member] | 65% to 75% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	232	336
1.00x - 1.20x [Member] | 76% to 80% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	111	98
1.00x - 1.20x [Member] | Greater than 80% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	740	880
Less than 1.00x [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	1,481	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	538	564
Less than 1.00x [Member] | 65% to 75% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	280	386
Less than 1.00x [Member] | 76% to 80% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	226	226
Less than 1.00x [Member] | Greater than 80% [Member]
Commercial Mortgage Loans - by Credit Quality Indicators with Estimated Fair Value:
Commercial mortgage loans	$ 437	$ 380