Fair Value (Financial Instruments Carried at Other Than Fair Value) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Assets
Policy loans	$ 1,216	$ 1,216
Liabilities
Separate account liabilities	94,020	86,114
Estimated Fair Value [Member]
Assets
Held-for-investment	6,752	7,009
Held-for-sale	63	0
Mortgage loans, net	6,815	7,009
Policy loans	1,287	1,311
Real estate joint ventures	103	101
Other Limited Partnership Interests	96	103
Other invested assets	512	548
Premiums, reinsurance and other receivables	7,259	7,000
Liabilities
Policyholder account balances	22,933	24,520
Long-term Debt	999	1,076
Other Liabilities	435	237
Separate account liabilities	1,373	1,296
Estimated Fair Value [Member] \| Mortgage Loan Commitments [Member]
Assets
Off-balance sheet commitments		1
Liabilities
Off-balance sheet commitments	(1)
Estimated Fair Value [Member] \| Commitments to Fund Bank Credit Facilities and Private Corporate Bond Investments [Member]
Assets
Off-balance sheet commitments	3	6
Estimated Fair Value [Member] \| Level 1 [Member]
Assets
Held-for-investment	0	0
Held-for-sale	0	0
Mortgage loans, net	0	0
Policy loans	0	0
Real estate joint ventures	0	0
Other Limited Partnership Interests	0	0
Other invested assets	0	0
Premiums, reinsurance and other receivables	0	0
Liabilities
Policyholder account balances	0	0
Long-term Debt	0	0
Other Liabilities	0	0
Separate account liabilities	0	0
Estimated Fair Value [Member] \| Level 1 [Member] \| Mortgage Loan Commitments [Member]
Assets
Off-balance sheet commitments		0
Liabilities
Off-balance sheet commitments	0
Estimated Fair Value [Member] \| Level 1 [Member] \| Commitments to Fund Bank Credit Facilities and Private Corporate Bond Investments [Member]
Assets
Off-balance sheet commitments	0	0
Estimated Fair Value [Member] \| Level 2 [Member]
Assets
Held-for-investment	0	0
Held-for-sale	0	0
Mortgage loans, net	0	0
Policy loans	869	861
Real estate joint ventures	0	0
Other Limited Partnership Interests	0	0
Other invested assets	512	548
Premiums, reinsurance and other receivables	506	86
Liabilities
Policyholder account balances	0	0
Long-term Debt	999	1,076
Other Liabilities	278	81
Separate account liabilities	1,373	1,296
Estimated Fair Value [Member] \| Level 2 [Member] \| Mortgage Loan Commitments [Member]
Assets
Off-balance sheet commitments		0
Liabilities
Off-balance sheet commitments	0
Estimated Fair Value [Member] \| Level 2 [Member] \| Commitments to Fund Bank Credit Facilities and Private Corporate Bond Investments [Member]
Assets
Off-balance sheet commitments	3	6
Estimated Fair Value [Member] \| Level 3 [Member]
Assets
Held-for-investment	6,752	7,009
Held-for-sale	63	0
Mortgage loans, net	6,815	7,009
Policy loans	418	450
Real estate joint ventures	103	101
Other Limited Partnership Interests	96	103
Other invested assets	0	0
Premiums, reinsurance and other receivables	6,753	6,914
Liabilities
Policyholder account balances	22,933	24,520
Long-term Debt	0	0
Other Liabilities	157	156
Separate account liabilities	0	0
Estimated Fair Value [Member] \| Level 3 [Member] \| Mortgage Loan Commitments [Member]
Assets
Off-balance sheet commitments		1
Liabilities
Off-balance sheet commitments	(1)
Estimated Fair Value [Member] \| Level 3 [Member] \| Commitments to Fund Bank Credit Facilities and Private Corporate Bond Investments [Member]
Assets
Off-balance sheet commitments	0	0
Carrying Value [Member]
Assets
Held-for-investment	6,390	6,491
Held-for-sale	63	0
Mortgage loans, net	6,453	6,491
Policy loans	1,216	1,216
Real estate joint ventures	56	59
Other Limited Partnership Interests	85	94
Other invested assets	455	432
Premiums, reinsurance and other receivables	6,541	6,015
Liabilities
Policyholder account balances	21,255	22,613
Long-term Debt	790	791
Other Liabilities	435	237
Separate account liabilities	1,373	1,296
Carrying Value [Member] \| Mortgage Loan Commitments [Member]
Assets
Off-balance sheet commitments		0
Liabilities
Off-balance sheet commitments	0
Carrying Value [Member] \| Commitments to Fund Bank Credit Facilities and Private Corporate Bond Investments [Member]
Assets
Off-balance sheet commitments	$ 0	$ 0

Total amount of mortgage loans not valued on a recurring basis as of the balance sheet date.

No definition available.

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- Definition

Fair value portion of mortgage loans held-for-investment.

+ References

No definition available.

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- Definition

Fair value portion of other investments not otherwise specified in the taxonomy.

+ References

No definition available.

+ Details

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Balance Type:	debit
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- Definition

The fair value portion of investments in other limited partnership interests.

+ References

No definition available.

+ Details

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Namespace Prefix:	micc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of the liability of policyholders for deposits held under the terms of insurance contracts.

+ References

No definition available.

+ Details

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Namespace Prefix:	micc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

The fair value of financial assets, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=28364263&loc=d3e13433-108611

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- Definition

The fair value of financial liabilities, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

+ References

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- Definition

Amount before allowance of loans made to policy and contract holders using their life insurance contracts' cash value or separate accounts as collateral. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums over and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7(a)(7))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.1(e))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Subparagraph e

-Article 7

+ Details

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- Definition

The fair value amount of long-term debt 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.

+ References

No definition available.

+ Details

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- Definition

Fair value portion of mortgage loans held-for-sale.

+ References

No definition available.

+ Details

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- Definition

Fair value portion of other liabilities.

+ References

No definition available.

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- Definition

The book value of investments in real estate joint ventures including direct and indirect investments.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.1(d))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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- Definition

Fair value portion of receivables, including, but not limited to, trade account receivables, note receivables, and loan receivables.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.3)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 3, 4

-Article 5

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- Definition

Amount of liability for variable contracts that meet specified criteria that are backed by assets held in separate accounts and carried at the fair value of those assets.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 80

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6484091&loc=d3e19268-158472

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-Glossary Separate Account

-URI http://asc.fasb.org/extlink&oid=6524887

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 80

-Section 50

-Paragraph 1

-Subparagraph (b)(1)

-URI http://asc.fasb.org/extlink&oid=6484115&loc=d3e19393-158473

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 18

-Article 7

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