Condensed Financial Information of Registrant (Details 3) (Parent Company [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2009	Dec. 31, 2010
Loans to Subsidiaries
Loans to subsidiaries	$ 0		$ 1,275
Loans to Subsidiaries - Surplus Note MLIC $775 Million Maturing Dec 2011 [Member]
Loans to Subsidiaries
Loans to Subsidiaries Instrument, Interest Rate Terms	Six-month LIBOR	6-month LIBOR
Loans to Subsidiaries Instrument, Basis Spread on Variable Rate	1.80%	1.80%
Loans to Subsidiaries Instrument, Maturity Date	December 31, 2011
Loans to subsidiaries	0	775	775
Loans to Subsidiaries - MLIC $400 Million Maturing Dec 2032 [Member]
Loans to Subsidiaries
Loans to Subsidiaries Instrument, Interest Rate Stated Percentage	7.13%
Loans to Subsidiaries Instrument, Maturity Date	December 15, 2032
Loans to subsidiaries	0		400
Loans to Subsidiaries - MLIC $100 Million Maturing Jan 2033 [Member]
Loans to Subsidiaries
Loans to Subsidiaries Instrument, Interest Rate Stated Percentage	7.13%
Loans to Subsidiaries Instrument, Maturity Date	January 15, 2033
Loans to subsidiaries	$ 0		$ 100

For advances to affiliates, interest rate stated in the contractual agreement.

No definition available.

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- Definition

For advances to affiliates, description of the interest rate as being fixed or variable, and, if variable, identification of the index or rate on which the interest rate is based and the number of points or percentage added to that index or rate to set the rate, and other pertinent information, such as frequency of rate resets.

+ References

No definition available.

+ Details

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- Definition

Date when the advance to affiliate is scheduled to be fully repaid, which may be presented in a variety of ways (year, month and year, day, month and year, quarter, etc.).

+ References

No definition available.

+ Details

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- Definition

For advances to affiliates, The percentage points added to the reference rate to compute the variable rate on the interest rate stated in the contractual agreement.

+ References

No definition available.

+ Details

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- Definition

Long-Term advances receivable from a party that is affiliated with the reporting entity by means of direct or indirect ownership. This does not include advances to clients.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 2

-Article 6

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 4

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6361293&loc=d3e6812-107765

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.6-04.2)

-URI http://asc.fasb.org/extlink&oid=6488278&loc=d3e603758-122996

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