Investments (Details 45) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	$ 378,005	$ 350,271
Mortgage Loans on Real Estate, Commercial and Consumer, Net	57,884	56,915
Estimated Fair Value	6,896	7,273
MRSC collateral financing arrangement [Member]
Variable Interest Entity [Line Items]
Mortgage Loans on Real Estate, Commercial and Consumer, Net	49	49
Cash and cash equivalents	22	59
Estimated Fair Value	3,420	3,333
Fixed maturity securities [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	378,005	350,271
U.S. corporate securities [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	113,942	105,785
U.S. corporate securities [Member] \| MRSC collateral financing arrangement [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	897	833
Foreign corporate securities [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	65,257	64,018
Foreign corporate securities [Member] \| MRSC collateral financing arrangement [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	91	126
RMBS [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	40,591	42,637
RMBS [Member] \| MRSC collateral financing arrangement [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	527	502
CMBS [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	19,440	19,069
CMBS [Member] \| MRSC collateral financing arrangement [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	273	369
ABS [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	15,005	12,979
ABS [Member] \| MRSC collateral financing arrangement [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	1,528	1,356
State and political subdivision securities [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	14,917	13,235
State and political subdivision securities [Member] \| MRSC collateral financing arrangement [Member]
Variable Interest Entity [Line Items]
Available-for-sale Securities, Debt Securities	$ 33	$ 39

Amount of debt securities categorized neither as held-to-maturity nor trading.

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15C

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 137

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 16

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

-Section 50

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

-Publisher FASB

-Name Accounting Standards Codification

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

-Publisher FASB

-Name Accounting Standards Codification

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15D

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+ 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.

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