FAIR VALUE MEASUREMENTS - Significant Unobservable Inputs Used in the Valuation of Available-for-sale Investments and Derivatives (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Liabilities:
Length of Volatility of Japanese Yen to US Dollar Exchange Rate	10 years
Level 3
Assets:
Total assets	3,596
Liabilities:
Total liabilities	399
Level 3 | Credit default swaps
Assets:
Asset derivatives	2
Level 3 | Consensus pricing valuation technique | Mortgage- and asset-backed Securities | Fixed Maturities
Assets:
Available-for-sale Securities	338
Level 3 | Consensus pricing valuation technique | Banks/financial Institutions | Fixed Maturities
Assets:
Available-for-sale Securities	580
Level 3 | Consensus pricing valuation technique | Other Corporate | Fixed Maturities
Assets:
Available-for-sale Securities	411
Level 3 | Discounted cash flow valuation technique | Public Utilities | Fixed Maturities
Assets:
Available-for-sale Securities	420
Level 3 | Discounted cash flow valuation technique | Sovereign and Supranational | Fixed Maturities
Assets:
Available-for-sale Securities	418
Level 3 | Discounted cash flow valuation technique | Banks/financial Institutions | Fixed Maturities
Assets:
Available-for-sale Securities	444
Level 3 | Discounted cash flow valuation technique | Banks/financial Institutions | Perpetual securities
Assets:
Available-for-sale Securities	215
Level 3 | Discounted cash flow valuation technique | Other Corporate | Fixed Maturities
Assets:
Available-for-sale Securities	575
Level 3 | Discounted cash flow valuation technique | Interest rate swaps
Assets:
Asset derivatives	32	[1]
Liabilities:
Swaps	3	[1]
Level 3 | Discounted cash flow valuation technique | Credit default swaps
Assets:
Asset derivatives	2
Liabilities:
Swaps	67	[1]
Level 3 | Net Asset Value Valuation Technique | Equity securities
Assets:
Available-for-sale Securities	4
Level 3 | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Discounted cash flow valuation technique | Foreign currency swaps
Assets:
Asset derivatives	51	[2]
Liabilities:
Swaps	118	[2]
Level 3 | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Discounted cash flow valuation technique | Foreign currency swaps
Assets:
Asset derivatives	4	[2]
Liabilities:
Swaps	60	[2]
Level 3 | Fair Value, Unobservable Input, Interest Rates (USD), interest rates (JPY), and Foreign Exchange Rates [Member] | Discounted cash flow valuation technique | Foreign currency swaps
Assets:
Asset derivatives	102	[2]
Liabilities:
Swaps	151	[2]
Level 3 | Liability [Member] | Lower Limit | Interest rate swaps
Unobservable Inputs
Base correlation	49.00%
CDS spreads	0.91%
Level 3 | Liability [Member] | Lower Limit | Credit default swaps
Unobservable Inputs
Base correlation	49.00%
CDS spreads	0.91%
Level 3 | Liability [Member] | Upper Limit | Interest rate swaps
Unobservable Inputs
Base correlation	50.00%
CDS spreads	1.52%
Level 3 | Liability [Member] | Upper Limit | Credit default swaps
Unobservable Inputs
Base correlation	50.00%
CDS spreads	1.52%
Level 3 | Liability [Member] | Weighted Average | Interest rate swaps
Unobservable Inputs
Recovery rate	37.00%
Level 3 | Liability [Member] | Weighted Average | Credit default swaps
Unobservable Inputs
Recovery rate	37.00%
Level 3 | Liability [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Foreign currency swaps
Unobservable Inputs
Foreign exchange rates	20.65%
Level 3 | Liability [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Lower Limit | Foreign currency swaps
Unobservable Inputs
CDS spreads	0.22%
Level 3 | Liability [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Upper Limit | Foreign currency swaps
Unobservable Inputs
CDS spreads	1.41%
Level 3 | Liability [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Lower Limit | Foreign currency swaps
Unobservable Inputs
CDS spreads	0.25%
Level 3 | Liability [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Upper Limit | Foreign currency swaps
Unobservable Inputs
CDS spreads	1.86%
Level 3 | Liability [Member] | Fair Value, Unobservable Input, Interest Rates (USD), interest rates (JPY), and Foreign Exchange Rates [Member] | Foreign currency swaps
Unobservable Inputs
Foreign exchange rates	20.65%
Level 3 | Liability [Member] | United States of America, Dollars | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Lower Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	1.84%
Level 3 | Liability [Member] | United States of America, Dollars | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Upper Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	2.84%
Level 3 | Liability [Member] | United States of America, Dollars | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Lower Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	1.84%
Level 3 | Liability [Member] | United States of America, Dollars | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Upper Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	2.84%
Level 3 | Liability [Member] | United States of America, Dollars | Fair Value, Unobservable Input, Interest Rates (USD), interest rates (JPY), and Foreign Exchange Rates [Member] | Lower Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	1.84%
Level 3 | Liability [Member] | United States of America, Dollars | Fair Value, Unobservable Input, Interest Rates (USD), interest rates (JPY), and Foreign Exchange Rates [Member] | Upper Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	2.84%
Level 3 | Liability [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Lower Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	0.84%
Level 3 | Liability [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Upper Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	2.05%
Level 3 | Liability [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Lower Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	0.84%
Level 3 | Liability [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Upper Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	2.05%
Level 3 | Liability [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), interest rates (JPY), and Foreign Exchange Rates [Member] | Lower Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	0.84%
Level 3 | Liability [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), interest rates (JPY), and Foreign Exchange Rates [Member] | Upper Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	2.05%
Level 3 | Assets [Member] | Public Utilities
Unobservable Inputs
Historical Volatility Rate	7.36%
Level 3 | Assets [Member] | Sovereign and Supranational
Unobservable Inputs
Historical Volatility Rate	7.36%
Level 3 | Assets [Member] | Banks/financial Institutions
Unobservable Inputs
Historical Volatility Rate	7.36%
Level 3 | Assets [Member] | Banks/financial Institutions | Perpetual securities
Unobservable Inputs
Historical Volatility Rate	7.36%
Level 3 | Assets [Member] | Other Corporate
Unobservable Inputs
Historical Volatility Rate	7.36%
Level 3 | Assets [Member] | Lower Limit | Equity securities
Unobservable Inputs
Offered quotes (in dollars per share)	2
Level 3 | Assets [Member] | Lower Limit | Interest rate swaps
Unobservable Inputs
Base correlation	49.00%
CDS spreads	0.91%
Level 3 | Assets [Member] | Lower Limit | Credit default swaps
Unobservable Inputs
Base correlation	49.00%
CDS spreads	0.91%
Level 3 | Assets [Member] | Upper Limit | Equity securities
Unobservable Inputs
Offered quotes (in dollars per share)	943
Level 3 | Assets [Member] | Upper Limit | Interest rate swaps
Unobservable Inputs
Base correlation	50.00%
CDS spreads	1.52%
Level 3 | Assets [Member] | Upper Limit | Credit default swaps
Unobservable Inputs
Base correlation	50.00%
CDS spreads	1.52%
Level 3 | Assets [Member] | Weighted Average | Equity securities
Unobservable Inputs
Offered quotes (in dollars per share)	8
Level 3 | Assets [Member] | Weighted Average | Interest rate swaps
Unobservable Inputs
Recovery rate	37.00%
Level 3 | Assets [Member] | Weighted Average | Credit default swaps
Unobservable Inputs
Recovery rate	37.00%
Level 3 | Assets [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Foreign currency swaps
Unobservable Inputs
Foreign exchange rates	20.65%
Level 3 | Assets [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Lower Limit | Foreign currency swaps
Unobservable Inputs
CDS spreads	0.12%
Level 3 | Assets [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Upper Limit | Foreign currency swaps
Unobservable Inputs
CDS spreads	1.17%
Level 3 | Assets [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Lower Limit | Foreign currency swaps
Unobservable Inputs
CDS spreads	0.12%
Level 3 | Assets [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Upper Limit | Foreign currency swaps
Unobservable Inputs
CDS spreads	1.26%
Level 3 | Assets [Member] | Fair Value, Unobservable Input, Interest Rates (USD), interest rates (JPY), and Foreign Exchange Rates [Member] | Foreign currency swaps
Unobservable Inputs
Foreign exchange rates	20.65%
Level 3 | Assets [Member] | United States of America, Dollars | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Lower Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	1.84%
Level 3 | Assets [Member] | United States of America, Dollars | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Upper Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	2.84%
Level 3 | Assets [Member] | United States of America, Dollars | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Lower Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	1.84%
Level 3 | Assets [Member] | United States of America, Dollars | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Upper Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	2.84%
Level 3 | Assets [Member] | United States of America, Dollars | Fair Value, Unobservable Input, Interest Rates (USD), interest rates (JPY), and Foreign Exchange Rates [Member] | Lower Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	1.84%
Level 3 | Assets [Member] | United States of America, Dollars | Fair Value, Unobservable Input, Interest Rates (USD), interest rates (JPY), and Foreign Exchange Rates [Member] | Upper Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	2.84%
Level 3 | Assets [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Lower Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	0.84%
Level 3 | Assets [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Upper Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	2.05%
Level 3 | Assets [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Lower Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	0.84%
Level 3 | Assets [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Upper Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	2.05%
Level 3 | Assets [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), interest rates (JPY), and Foreign Exchange Rates [Member] | Lower Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	0.84%
Level 3 | Assets [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), interest rates (JPY), and Foreign Exchange Rates [Member] | Upper Limit | Foreign currency swaps
Unobservable Inputs
Interest rates	2.05%

[1] Weighted-average range of base correlations for our bespoke tranches for attachment and detachment points corresponding to market indices

[2] Inputs derived from U.S. long-term rates to accommodate long maturity nature of our swaps