Investments (Details 7) (USD $) In Millions, unless otherwise specified	Sep. 30, 2011	Dec. 31, 2010
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Estimated fair value	$ 170,097	$ 159,660
% of Total	100.00%	100.00%
Vintage Year, 2005 [Member] \| Alternative residential mortgage loans [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Estimated fair value	1,632	1,576
% of Total	35.70%	37.30%
Vintage Year, 2006 [Member] \| Alternative residential mortgage loans [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Estimated fair value	1,294	1,013
% of Total	28.30%	24.00%
Vintage Year, 2007 [Member] \| Alternative residential mortgage loans [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Estimated fair value	997	922
% of Total	21.80%	21.80%
Vintage Year, 2008 [Member] \| Alternative residential mortgage loans [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Estimated fair value	0	7
% of Total	0.00%	0.20%
Vintage Year, 2009 [Member] \| Alternative residential mortgage loans [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Estimated fair value	615	671
% of Total	13.50%	15.90%
Vintage Year, 2010 [Member] \| Alternative residential mortgage loans [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Estimated fair value	34	32
% of Total	0.70%	0.80%
Vintage Year, 2011 [Member] \| Alternative residential mortgage loans [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Estimated fair value	0	0
% of Total	0.00%	0.00%
Alternative residential mortgage loans [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Estimated fair value	$ 4,572	$ 4,221
% of Total	100.00%	100.00%

This item represents disclosure of all significant concentrations of credit risk or market risk arising from the subject financial instrument (as defined), whether from an individual counterparty or groups of counterparties.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Available-for-Sale Securities

-URI http://asc.fasb.org/extlink&oid=6505594

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 107

-Paragraph 15A

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 107

-Paragraph 15C

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Trading Securities

-URI http://asc.fasb.org/extlink&oid=6526789

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6379932&loc=d3e22054-111558

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 107

-Paragraph 15D

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 7

-Section 03

-Paragraph 1

-Subparagraph a, f, g

+ Details