FAIR VALUE MEASUREMENTS - Fair Value Hierarchy Levels of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Level 3
Assets:
Total assets	$ 3,596
Liabilities:
Total liabilities	399
Level 3 \| Credit default swaps
Assets:
Swaps	2
Fair Value, Measurements, Recurring
Assets:
Available-for-sale Securities	61,578	54,036
Swaps	345	375
Cash and cash equivalents	2,041	2,249
Total assets	63,964	56,660
Liabilities:
Total liabilities	934	531
Fair Value, Measurements, Recurring \| Interest rate swaps
Assets:
Swaps	32	34
Liabilities:
Swaps	3	4
Fair Value, Measurements, Recurring \| Foreign currency swaps
Assets:
Swaps	311	341
Liabilities:
Swaps	329	397
Fair Value, Measurements, Recurring \| Foreign currency forwards
Liabilities:
Swaps	535
Fair Value, Measurements, Recurring \| Credit default swaps
Assets:
Swaps	2
Liabilities:
Swaps	67	130
Fair Value, Measurements, Recurring \| Fixed Maturities
Assets:
Available-for-sale Securities	57,253	47,572
Fair Value, Measurements, Recurring \| Fixed Maturities \| Government and Agencies Debt Securities
Assets:
Available-for-sale Securities	12,997	11,813
Fair Value, Measurements, Recurring \| Fixed Maturities \| Municipalities
Assets:
Available-for-sale Securities	1,195	1,159
Fair Value, Measurements, Recurring \| Fixed Maturities \| Mortgage- and asset-backed Securities
Assets:
Available-for-sale Securities	1,031	1,338
Fair Value, Measurements, Recurring \| Fixed Maturities \| Public Utilities
Assets:
Available-for-sale Securities	8,497	7,225
Fair Value, Measurements, Recurring \| Fixed Maturities \| Sovereign and Supranational
Assets:
Available-for-sale Securities	2,072	2,308
Fair Value, Measurements, Recurring \| Fixed Maturities \| Banks/financial Institutions
Assets:
Available-for-sale Securities	7,634	7,453
Fair Value, Measurements, Recurring \| Fixed Maturities \| Other Corporate
Assets:
Available-for-sale Securities	23,827	16,276
Fair Value, Measurements, Recurring \| Perpetual securities
Assets:
Available-for-sale Securities	4,302	6,439
Fair Value, Measurements, Recurring \| Perpetual securities \| Banks/financial Institutions
Assets:
Available-for-sale Securities	3,950	6,078
Fair Value, Measurements, Recurring \| Perpetual securities \| Other Corporate
Assets:
Available-for-sale Securities	352	361
Fair Value, Measurements, Recurring \| Equity securities
Assets:
Available-for-sale Securities	23	25
Fair Value, Measurements, Recurring \| Level 1
Assets:
Available-for-sale Securities	12,278	11,107
Swaps	0	0
Cash and cash equivalents	2,041	2,249
Total assets	14,319	13,356
Liabilities:
Total liabilities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Interest rate swaps
Assets:
Swaps	0	0
Liabilities:
Swaps	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Foreign currency swaps
Assets:
Swaps	0	0
Liabilities:
Swaps	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Foreign currency forwards
Liabilities:
Swaps	0
Fair Value, Measurements, Recurring \| Level 1 \| Credit default swaps
Assets:
Swaps	0
Liabilities:
Swaps	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Fixed Maturities
Assets:
Available-for-sale Securities	12,265	11,092
Fair Value, Measurements, Recurring \| Level 1 \| Fixed Maturities \| Government and Agencies Debt Securities
Assets:
Available-for-sale Securities	12,265	11,092
Fair Value, Measurements, Recurring \| Level 1 \| Fixed Maturities \| Municipalities
Assets:
Available-for-sale Securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Fixed Maturities \| Mortgage- and asset-backed Securities
Assets:
Available-for-sale Securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Fixed Maturities \| Public Utilities
Assets:
Available-for-sale Securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Fixed Maturities \| Sovereign and Supranational
Assets:
Available-for-sale Securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Fixed Maturities \| Banks/financial Institutions
Assets:
Available-for-sale Securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Fixed Maturities \| Other Corporate
Assets:
Available-for-sale Securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Perpetual securities
Assets:
Available-for-sale Securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Perpetual securities \| Banks/financial Institutions
Assets:
Available-for-sale Securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Perpetual securities \| Other Corporate
Assets:
Available-for-sale Securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Equity securities
Assets:
Available-for-sale Securities	13	15
Fair Value, Measurements, Recurring \| Level 2
Assets:
Available-for-sale Securities	45,895	38,970
Swaps	154	0
Cash and cash equivalents	0	0
Total assets	46,049	38,970
Liabilities:
Total liabilities	535	0
Fair Value, Measurements, Recurring \| Level 2 \| Interest rate swaps
Assets:
Swaps	0	0
Liabilities:
Swaps	0	0
Fair Value, Measurements, Recurring \| Level 2 \| Foreign currency swaps
Assets:
Swaps	154	0
Liabilities:
Swaps	0	0
Fair Value, Measurements, Recurring \| Level 2 \| Foreign currency forwards
Liabilities:
Swaps	535
Fair Value, Measurements, Recurring \| Level 2 \| Credit default swaps
Assets:
Swaps	0
Liabilities:
Swaps	0	0
Fair Value, Measurements, Recurring \| Level 2 \| Fixed Maturities
Assets:
Available-for-sale Securities	41,802	33,051
Fair Value, Measurements, Recurring \| Level 2 \| Fixed Maturities \| Government and Agencies Debt Securities
Assets:
Available-for-sale Securities	732	721
Fair Value, Measurements, Recurring \| Level 2 \| Fixed Maturities \| Municipalities
Assets:
Available-for-sale Securities	1,195	1,159
Fair Value, Measurements, Recurring \| Level 2 \| Fixed Maturities \| Mortgage- and asset-backed Securities
Assets:
Available-for-sale Securities	693	944
Fair Value, Measurements, Recurring \| Level 2 \| Fixed Maturities \| Public Utilities
Assets:
Available-for-sale Securities	8,077	6,803
Fair Value, Measurements, Recurring \| Level 2 \| Fixed Maturities \| Sovereign and Supranational
Assets:
Available-for-sale Securities	1,654	1,874
Fair Value, Measurements, Recurring \| Level 2 \| Fixed Maturities \| Banks/financial Institutions
Assets:
Available-for-sale Securities	6,610	6,379
Fair Value, Measurements, Recurring \| Level 2 \| Fixed Maturities \| Other Corporate
Assets:
Available-for-sale Securities	22,841	15,171
Fair Value, Measurements, Recurring \| Level 2 \| Perpetual securities
Assets:
Available-for-sale Securities	4,087	5,913
Fair Value, Measurements, Recurring \| Level 2 \| Perpetual securities \| Banks/financial Institutions
Assets:
Available-for-sale Securities	3,735	5,552
Fair Value, Measurements, Recurring \| Level 2 \| Perpetual securities \| Other Corporate
Assets:
Available-for-sale Securities	352	361
Fair Value, Measurements, Recurring \| Level 2 \| Equity securities
Assets:
Available-for-sale Securities	6	6
Fair Value, Measurements, Recurring \| Level 3
Assets:
Available-for-sale Securities	3,405	3,959
Swaps	191	375
Cash and cash equivalents	0	0
Total assets	3,596	4,334
Liabilities:
Total liabilities	399	531
Fair Value, Measurements, Recurring \| Level 3 \| Interest rate swaps
Assets:
Swaps	32	34
Liabilities:
Swaps	3	4
Fair Value, Measurements, Recurring \| Level 3 \| Foreign currency swaps
Assets:
Swaps	157	341
Liabilities:
Swaps	329	397
Fair Value, Measurements, Recurring \| Level 3 \| Foreign currency forwards
Liabilities:
Swaps	0
Fair Value, Measurements, Recurring \| Level 3 \| Credit default swaps
Liabilities:
Swaps	67	130
Fair Value, Measurements, Recurring \| Level 3 \| Fixed Maturities
Assets:
Available-for-sale Securities	3,186	3,429
Fair Value, Measurements, Recurring \| Level 3 \| Fixed Maturities \| Government and Agencies Debt Securities
Assets:
Available-for-sale Securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Fixed Maturities \| Municipalities
Assets:
Available-for-sale Securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Fixed Maturities \| Mortgage- and asset-backed Securities
Assets:
Available-for-sale Securities	338	394
Fair Value, Measurements, Recurring \| Level 3 \| Fixed Maturities \| Public Utilities
Assets:
Available-for-sale Securities	420	422
Fair Value, Measurements, Recurring \| Level 3 \| Fixed Maturities \| Sovereign and Supranational
Assets:
Available-for-sale Securities	418	434
Fair Value, Measurements, Recurring \| Level 3 \| Fixed Maturities \| Banks/financial Institutions
Assets:
Available-for-sale Securities	1,024	1,074
Fair Value, Measurements, Recurring \| Level 3 \| Fixed Maturities \| Other Corporate
Assets:
Available-for-sale Securities	986	1,105
Fair Value, Measurements, Recurring \| Level 3 \| Perpetual securities
Assets:
Available-for-sale Securities	215	526
Fair Value, Measurements, Recurring \| Level 3 \| Perpetual securities \| Banks/financial Institutions
Assets:
Available-for-sale Securities	215	526
Fair Value, Measurements, Recurring \| Level 3 \| Perpetual securities \| Other Corporate
Assets:
Available-for-sale Securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Equity securities
Assets:
Available-for-sale Securities	$ 4	$ 4

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 represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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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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- Definition

Fair values as of the balance sheet date of all assets resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements.

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- Definition

Derivative instrument obligations meeting the definition of a liability which the Company is a party to as of the balance sheet date.

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