This represents the recorded investment for impaired mortgage loans held-for-investment.

No definition available.

Name:	met_RecordedInvestmentForImpairedMortgageLoansHeldForInvestment
Namespace Prefix:	met_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The reserve to cover probable credit losses related to specifically identified fixed maturity real estate loans as well as probable credit losses inherent in the remainder of that loan portfolio.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 60

-Paragraph 47

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 310

-Section 45

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6873192&loc=d3e21338-158488

+ Details

Name:	us-gaap_AllowanceForLoanAndLeaseLossesRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5212-111524

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 17

-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5258-111524

+ Details

Name:	us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

+ Details

Name:	us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 14A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953550-111524

+ Details

Name:	us-gaap_ImpairedFinancingReceivableRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses.

+ References

+ Details

Name:	us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_LoanAndLeaseReceivablesImpairedAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Investments (Impaired Mortgage Loans) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011
Impaired Mortgage Loans
Unpaid Principal Balance	$ 739		$ 750
Valuation allowances	332	446	347	481
Recorded Investment	621		616
Average Investment	719	516
Interest Income	4	4
Loans with a Valuation Allowance [Member]
Impaired Mortgage Loans
Unpaid Principal Balance	364		568
Recorded Investment	347		556
Valuation allowances	82		117
Recorded Investment	265		439
Loans Without Valuation Allowances [Member]
Impaired Mortgage Loans
Unpaid Principal Balance	375		182
Recorded Investment	356		177
Commercial mortgage loans portfolio segment [Member]
Impaired Mortgage Loans
Unpaid Principal Balance	563		548
Valuation allowances	275	368	293	398
Recorded Investment	472		445
Average Investment	536	273
Interest Income	3	3
Commercial mortgage loans portfolio segment [Member] \| Loans with a Valuation Allowance [Member]
Impaired Mortgage Loans
Unpaid Principal Balance	261		445
Recorded Investment	245		436
Valuation allowances	61		94
Recorded Investment	184		342
Commercial mortgage loans portfolio segment [Member] \| Loans Without Valuation Allowances [Member]
Impaired Mortgage Loans
Unpaid Principal Balance	302		103
Recorded Investment	288		103
Agricultural [Member]
Impaired Mortgage Loans
Unpaid Principal Balance	162		189
Valuation allowances	54	75	52	81
Recorded Investment	137		160
Average Investment	169	229
Interest Income	1	1
Agricultural [Member] \| Loans with a Valuation Allowance [Member]
Impaired Mortgage Loans
Unpaid Principal Balance	91		110
Recorded Investment	90		107
Valuation allowances	19		21
Recorded Investment	71		86
Agricultural [Member] \| Loans Without Valuation Allowances [Member]
Impaired Mortgage Loans
Unpaid Principal Balance	71		79
Recorded Investment	66		74
Residential [Member]
Impaired Mortgage Loans
Unpaid Principal Balance	14		13
Valuation allowances	3	3	2	2
Recorded Investment	12		11
Average Investment	14	14
Interest Income	0	0
Residential [Member] \| Loans with a Valuation Allowance [Member]
Impaired Mortgage Loans
Unpaid Principal Balance	12		13
Recorded Investment	12		13
Valuation allowances	2		2
Recorded Investment	10		11
Residential [Member] \| Loans Without Valuation Allowances [Member]
Impaired Mortgage Loans
Unpaid Principal Balance	2		0
Recorded Investment	$ 2		$ 0