Investments (Details 45) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	$ 350,271	$ 324,797
Mortgage Loans on Real Estate, Commercial and Consumer, Net	56,915	58,976
Estimated Fair Value	7,273	11,080
MRSC collateral financing arrangement [Member]
Variable Interest Entity [Line Items]
Mortgage Loans on Real Estate, Commercial and Consumer, Net	49	0
Cash and cash equivalents	59	3
Estimated Fair Value	3,333	3,333
Fixed maturity securities [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	350,271	324,797
U.S. corporate securities [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	105,785	91,772
U.S. corporate securities [Member] \| MRSC collateral financing arrangement [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	833	893
Foreign corporate securities [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	64,018	67,888
Foreign corporate securities [Member] \| MRSC collateral financing arrangement [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	126	139
Foreign government debt securities [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	52,536	42,002
Foreign government debt securities [Member] \| MRSC collateral financing arrangement [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	0	5
RMBS [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	42,637	45,852
RMBS [Member] \| MRSC collateral financing arrangement [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	502	547
CMBS [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	19,069	20,675
CMBS [Member] \| MRSC collateral financing arrangement [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	369	383
ABS [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	12,979	13,168
ABS [Member] \| MRSC collateral financing arrangement [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	1,356	1,333
State and political subdivision securities [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	13,235	10,129
State and political subdivision securities [Member] \| MRSC collateral financing arrangement [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	$ 39	$ 30

For an unclassified balance sheet, total of debt securities categorized neither as held-to-maturity nor trading.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

-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 FASB Staff Position (FSP)

-Number FAS115-1/124-1

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 22

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-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 6: 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 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

-Section 50

-Paragraph 2

-Subparagraph (b)-(g)

-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 137

-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 FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 16

-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 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

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

+ Details

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

+ References+ Details