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	9 Months Ended
	Sep. 30, 2012
Liabilities:
Length of Volatility of Japanese Yen to US Dollar Exchange Rate	10 years
Level 3
Assets:
Total assets	4,515
Liabilities:
Total liabilities	436
Level 3 | Consensus Pricing Valuation Technique | Mortgage- and asset-backed Securities
Assets:
Available-for-sale Securities	385
Level 3 | Consensus Pricing Valuation Technique | Banks/financial Institutions
Assets:
Available-for-sale Securities	810
Level 3 | Consensus Pricing Valuation Technique | Other Corporate
Assets:
Available-for-sale Securities	447
Level 3 | Discounted Cash Flow Valuation Technique | Public Utilities
Assets:
Available-for-sale Securities	449
Level 3 | Discounted Cash Flow Valuation Technique | Sovereign and Supranational
Assets:
Available-for-sale Securities	460
Level 3 | Discounted Cash Flow Valuation Technique | Banks/financial Institutions
Assets:
Available-for-sale Securities	613
Level 3 | Discounted Cash Flow Valuation Technique | Banks/financial Institutions | Perpetual Securities
Assets:
Available-for-sale Securities	370
Level 3 | Discounted Cash Flow Valuation Technique | Other Corporate
Assets:
Available-for-sale Securities	626
Level 3 | Discounted Cash Flow Valuation Technique | Interest rate swaps
Assets:
Asset derivatives	39
Liabilities:
Swaps	5
Level 3 | Discounted Cash Flow Valuation Technique | Credit default swaps
Liabilities:
Swaps	82
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	109
Liabilities:
Swaps	72
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	69
Liabilities:
Swaps	17
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	134
Liabilities:
Swaps	260
Level 3 | Liability [Member] | Lower Limit | Interest rate swaps
Unobservable Inputs
Base correlation	47.00%	[1]
CDS spreads	0.84%
Recovery rate	20.00%
Level 3 | Liability [Member] | Lower Limit | Credit default swaps
Unobservable Inputs
Base correlation	47.00%	[1]
CDS spreads	0.84%
Recovery rate	20.00%
Level 3 | Liability [Member] | Upper Limit | Interest rate swaps
Unobservable Inputs
Base correlation	59.00%	[1]
CDS spreads	1.92%
Recovery rate	70.00%
Level 3 | Liability [Member] | Upper Limit | Credit default swaps
Unobservable Inputs
Base correlation	59.00%	[1]
CDS spreads	1.92%
Recovery rate	70.00%
Level 3 | Liability [Member] | Weighted Average | Interest rate swaps
Unobservable Inputs
Recovery rate	40.00%
Level 3 | Liability [Member] | Weighted Average | Credit default swaps
Unobservable Inputs
Recovery rate	40.00%
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	20.22%	[2]
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	0.24%
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	1.40%
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	0.49%
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	2.59%
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	20.22%	[2]
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	1.70%	[3]
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	2.63%	[3]
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	1.70%	[3]
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	2.63%	[3]
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	1.70%	[3]
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	2.63%	[3]
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	0.77%	[4]
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	1.75%	[4]
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	0.77%	[4]
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	1.75%	[4]
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	0.77%	[4]
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	1.75%	[4]
Level 3 | Assets [Member] | Public Utilities
Unobservable Inputs
Historical Volatility Rate	5.30%
Level 3 | Assets [Member] | Sovereign and Supranational
Unobservable Inputs
Historical Volatility Rate	5.30%
Level 3 | Assets [Member] | Banks/financial Institutions
Unobservable Inputs
Historical Volatility Rate	5.30%
Level 3 | Assets [Member] | Banks/financial Institutions | Perpetual Securities
Unobservable Inputs
Historical Volatility Rate	5.30%
Level 3 | Assets [Member] | Other Corporate
Unobservable Inputs
Historical Volatility Rate	5.30%
Level 3 | Assets [Member] | Lower Limit | Equity Securities
Unobservable Inputs
Offered quotes (in dollars per share)	0
Level 3 | Assets [Member] | Lower Limit | Interest rate swaps
Unobservable Inputs
Base correlation	47.00%	[1]
CDS spreads	0.84%
Recovery rate	20.00%
Level 3 | Assets [Member] | Upper Limit | Equity Securities
Unobservable Inputs
Offered quotes (in dollars per share)	1,051
Level 3 | Assets [Member] | Upper Limit | Interest rate swaps
Unobservable Inputs
Base correlation	59.00%	[1]
CDS spreads	1.92%
Recovery rate	70.00%
Level 3 | Assets [Member] | Weighted Average | Equity Securities
Unobservable Inputs
Offered quotes (in dollars per share)	9
Level 3 | Assets [Member] | Weighted Average | Interest rate swaps
Unobservable Inputs
Recovery rate	40.00%
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	20.22%	[2]
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	0.16%
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	1.15%
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	0.21%
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	1.28%
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	20.22%	[2]
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	1.70%	[3]
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	2.63%	[3]
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	1.70%	[3]
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	2.63%	[3]
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	1.70%	[3]
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	2.63%	[3]
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	0.77%	[4]
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	1.75%	[4]
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	0.77%	[4]
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	1.75%	[4]
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	0.77%	[4]
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	1.75%	[4]

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

[2] Based on 10 year volatility of JPY/USD exchange rate

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

[4] Inputs derived from Japan long-term rates to accommodate long maturity nature of our swaps