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	Sep. 30, 2012	Dec. 31, 2011
Level 3
Assets:
Total assets	$ 4,515
Liabilities:
Total liabilities	436
Fair Value, Measurements, Recurring
Assets:
Swaps	384	375
Cash and cash equivalents	2,985	2,249
Total assets	64,360	56,660
Liabilities:
Total liabilities	447	531
Fair Value, Measurements, Recurring \| Interest rate swaps
Assets:
Swaps	39	34
Liabilities:
Swaps	5	4
Fair Value, Measurements, Recurring \| Foreign currency swaps
Assets:
Swaps	328	341
Liabilities:
Swaps	360	397
Fair Value, Measurements, Recurring \| Foreign currency forwards
Assets:
Swaps	17
Fair Value, Measurements, Recurring \| Credit default swaps
Liabilities:
Swaps	82	130
Fair Value, Measurements, Recurring \| Fixed Maturities
Assets:
Available-for-sale Securities	56,248	47,572
Fair Value, Measurements, Recurring \| Fixed Maturities \| Government and Agencies Debt Securities
Assets:
Available-for-sale Securities	14,659	11,813
Fair Value, Measurements, Recurring \| Fixed Maturities \| Municipalities
Assets:
Available-for-sale Securities	1,196	1,159
Fair Value, Measurements, Recurring \| Fixed Maturities \| Mortgage- and asset-backed Securities
Assets:
Available-for-sale Securities	1,205	1,338
Fair Value, Measurements, Recurring \| Fixed Maturities \| Public Utilities
Assets:
Available-for-sale Securities	8,307	7,225
Fair Value, Measurements, Recurring \| Fixed Maturities \| Sovereign and Supranational
Assets:
Available-for-sale Securities	2,587	2,308
Fair Value, Measurements, Recurring \| Fixed Maturities \| Banks/financial Institutions
Assets:
Available-for-sale Securities	8,283	7,453
Fair Value, Measurements, Recurring \| Fixed Maturities \| Other Corporate
Assets:
Available-for-sale Securities	20,011	16,276
Fair Value, Measurements, Recurring \| Perpetual Securities
Assets:
Available-for-sale Securities	4,719	6,439
Fair Value, Measurements, Recurring \| Perpetual Securities \| Banks/financial Institutions
Assets:
Available-for-sale Securities	4,348	6,078
Fair Value, Measurements, Recurring \| Perpetual Securities \| Other Corporate
Assets:
Available-for-sale Securities	371	361
Fair Value, Measurements, Recurring \| Equity Securities
Assets:
Available-for-sale Securities	24	25
Fair Value, Measurements, Recurring \| Level 1
Assets:
Swaps	0	0
Cash and cash equivalents	2,985	2,249
Total assets	16,843	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
Assets:
Swaps	0
Fair Value, Measurements, Recurring \| Level 1 \| Credit default swaps
Liabilities:
Swaps	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Fixed Maturities
Assets:
Available-for-sale Securities	13,845	11,092
Fair Value, Measurements, Recurring \| Level 1 \| Fixed Maturities \| Government and Agencies Debt Securities
Assets:
Available-for-sale Securities	13,845	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:
Swaps	33	0
Cash and cash equivalents	0	0
Total assets	43,002	38,970
Liabilities:
Total liabilities	11	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	16	0
Liabilities:
Swaps	11	0
Fair Value, Measurements, Recurring \| Level 2 \| Foreign currency forwards
Assets:
Swaps	17
Fair Value, Measurements, Recurring \| Level 2 \| Credit default swaps
Liabilities:
Swaps	0	0
Fair Value, Measurements, Recurring \| Level 2 \| Fixed Maturities
Assets:
Available-for-sale Securities	38,613	33,051
Fair Value, Measurements, Recurring \| Level 2 \| Fixed Maturities \| Government and Agencies Debt Securities
Assets:
Available-for-sale Securities	814	721
Fair Value, Measurements, Recurring \| Level 2 \| Fixed Maturities \| Municipalities
Assets:
Available-for-sale Securities	1,196	1,159
Fair Value, Measurements, Recurring \| Level 2 \| Fixed Maturities \| Mortgage- and asset-backed Securities
Assets:
Available-for-sale Securities	820	944
Fair Value, Measurements, Recurring \| Level 2 \| Fixed Maturities \| Public Utilities
Assets:
Available-for-sale Securities	7,858	6,803
Fair Value, Measurements, Recurring \| Level 2 \| Fixed Maturities \| Sovereign and Supranational
Assets:
Available-for-sale Securities	2,127	1,874
Fair Value, Measurements, Recurring \| Level 2 \| Fixed Maturities \| Banks/financial Institutions
Assets:
Available-for-sale Securities	6,860	6,379
Fair Value, Measurements, Recurring \| Level 2 \| Fixed Maturities \| Other Corporate
Assets:
Available-for-sale Securities	18,938	15,171
Fair Value, Measurements, Recurring \| Level 2 \| Perpetual Securities
Assets:
Available-for-sale Securities	4,349	5,913
Fair Value, Measurements, Recurring \| Level 2 \| Perpetual Securities \| Banks/financial Institutions
Assets:
Available-for-sale Securities	3,978	5,552
Fair Value, Measurements, Recurring \| Level 2 \| Perpetual Securities \| Other Corporate
Assets:
Available-for-sale Securities	371	361
Fair Value, Measurements, Recurring \| Level 2 \| Equity Securities
Assets:
Available-for-sale Securities	7	6
Fair Value, Measurements, Recurring \| Level 3
Assets:
Swaps	351	375
Cash and cash equivalents	0	0
Total assets	4,515	4,334
Liabilities:
Total liabilities	436	531
Fair Value, Measurements, Recurring \| Level 3 \| Interest rate swaps
Assets:
Swaps	39	34
Liabilities:
Swaps	5	4
Fair Value, Measurements, Recurring \| Level 3 \| Foreign currency swaps
Assets:
Swaps	312	341
Liabilities:
Swaps	349	397
Fair Value, Measurements, Recurring \| Level 3 \| Foreign currency forwards
Assets:
Swaps	0
Fair Value, Measurements, Recurring \| Level 3 \| Credit default swaps
Liabilities:
Swaps	82	130
Fair Value, Measurements, Recurring \| Level 3 \| Fixed Maturities
Assets:
Available-for-sale Securities	3,790	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	385	394
Fair Value, Measurements, Recurring \| Level 3 \| Fixed Maturities \| Public Utilities
Assets:
Available-for-sale Securities	449	422
Fair Value, Measurements, Recurring \| Level 3 \| Fixed Maturities \| Sovereign and Supranational
Assets:
Available-for-sale Securities	460	434
Fair Value, Measurements, Recurring \| Level 3 \| Fixed Maturities \| Banks/financial Institutions
Assets:
Available-for-sale Securities	1,423	1,074
Fair Value, Measurements, Recurring \| Level 3 \| Fixed Maturities \| Other Corporate
Assets:
Available-for-sale Securities	1,073	1,105
Fair Value, Measurements, Recurring \| Level 3 \| Perpetual Securities
Assets:
Available-for-sale Securities	370	526
Fair Value, Measurements, Recurring \| Level 3 \| Perpetual Securities \| Banks/financial Institutions
Assets:
Available-for-sale Securities	370	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
Carrying Value
Assets:
Swaps	384	375
Liabilities:
Swaps	$ 447	$ 531

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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