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	3 Months Ended
	Mar. 31, 2012
Liabilities:
Length of Volatility of Japanese Yen to US Dollar Exchange Rate	10 years
Level 3
Assets:
Total assets	3,926
Liabilities:
Total liabilities	419
Consensus Pricing Valuation Technique | Mortgage- and asset-backed Securities | Level 3
Assets:
Available-for-sale Securities	367
Consensus Pricing Valuation Technique | Banks/financial Institutions | Level 3
Assets:
Available-for-sale Securities	550
Consensus Pricing Valuation Technique | Other Corporate | Level 3
Assets:
Available-for-sale Securities	441
Discounted Cash Flow Valuation Technique | Public Utilities | Level 3
Assets:
Available-for-sale Securities	409
Discounted Cash Flow Valuation Technique | Sovereign and Supranational | Level 3
Assets:
Available-for-sale Securities	418
Discounted Cash Flow Valuation Technique | Banks/financial Institutions | Level 3
Assets:
Available-for-sale Securities	547
Discounted Cash Flow Valuation Technique | Banks/financial Institutions | Perpetual Securities | Level 3
Assets:
Available-for-sale Securities	325
Discounted Cash Flow Valuation Technique | Other Corporate | Level 3
Assets:
Available-for-sale Securities	594
Discounted Cash Flow Valuation Technique | Interest rate swaps | Level 3
Assets:
Asset Derivatives	31
Liabilities:
Swaps	3
Discounted Cash Flow Valuation Technique | Credit default swaps | Level 3
Liabilities:
Swaps	97
Net Asset Value Valuation Technique | Equity Securities | Level 3
Assets:
Available-for-sale Securities	4
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 | Level 3
Assets:
Asset Derivatives	81
Liabilities:
Swaps	91
Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Discounted Cash Flow Valuation Technique | Foreign currency swaps | Level 3
Assets:
Asset Derivatives	46
Liabilities:
Swaps	21
Fair Value, Unobservable Input, Interest Rates (USD), interest rates (JPY), and Foreign Exchange Rates [Member] | Discounted Cash Flow Valuation Technique | Foreign currency swaps | Level 3
Assets:
Asset Derivatives	113
Liabilities:
Swaps	207
Liability [Member] | Lower Limit | Interest rate swaps | Level 3
Unobservable Inputs
Base correlation	44.00%	[1]
CDS spreads	0.03%
Recovery rate	25.00%
Liability [Member] | Lower Limit | Credit default swaps | Level 3
Unobservable Inputs
Base correlation	44.00%	[1]
CDS spreads	0.03%
Recovery rate	25.00%
Liability [Member] | Upper Limit | Interest rate swaps | Level 3
Unobservable Inputs
Base correlation	52.00%	[1]
CDS spreads	16.73%
Recovery rate	70.00%
Liability [Member] | Upper Limit | Credit default swaps | Level 3
Unobservable Inputs
Base correlation	52.00%	[1]
CDS spreads	16.73%
Recovery rate	70.00%
Liability [Member] | Weighted Average | Interest rate swaps | Level 3
Unobservable Inputs
CDS spreads	1.36%
Recovery rate	40.00%
Liability [Member] | Weighted Average | Credit default swaps | Level 3
Unobservable Inputs
CDS spreads	1.36%
Recovery rate	40.00%
Liability [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Foreign currency swaps | Level 3
Unobservable Inputs
Foreign exchange rates	20.69%	[2]
Liability [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Lower Limit | Foreign currency swaps | Level 3
Unobservable Inputs
CDS spreads	0.14%
Liability [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Upper Limit | Foreign currency swaps | Level 3
Unobservable Inputs
CDS spreads	2.39%
Liability [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Weighted Average | Foreign currency swaps | Level 3
Unobservable Inputs
CDS spreads	1.28%
Liability [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Lower Limit | Foreign currency swaps | Level 3
Unobservable Inputs
CDS spreads	0.11%
Liability [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Upper Limit | Foreign currency swaps | Level 3
Unobservable Inputs
CDS spreads	3.59%
Liability [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Weighted Average | Foreign currency swaps | Level 3
Unobservable Inputs
CDS spreads	2.14%
Liability [Member] | Fair Value, Unobservable Input, Interest Rates (USD), interest rates (JPY), and Foreign Exchange Rates [Member] | Foreign currency swaps | Level 3
Unobservable Inputs
Foreign exchange rates	20.69%	[2]
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 | Level 3
Unobservable Inputs
Interest rates	2.29%	[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 | Level 3
Unobservable Inputs
Interest rates	3.05%	[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 | Level 3
Unobservable Inputs
Interest rates	2.29%	[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 | Level 3
Unobservable Inputs
Interest rates	3.05%	[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 | Level 3
Unobservable Inputs
Interest rates	2.29%	[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 | Level 3
Unobservable Inputs
Interest rates	3.05%	[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 | Level 3
Unobservable Inputs
Interest rates	1.04%	[4]
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 | Level 3
Unobservable Inputs
Interest rates	2.00%	[4]
Liability [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Lower Limit | Foreign currency swaps | Level 3
Unobservable Inputs
Interest rates	1.04%	[4]
Liability [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Upper Limit | Foreign currency swaps | Level 3
Unobservable Inputs
Interest rates	2.00%	[4]
Liability [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), interest rates (JPY), and Foreign Exchange Rates [Member] | Lower Limit | Foreign currency swaps | Level 3
Unobservable Inputs
Interest rates	1.04%	[4]
Liability [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), interest rates (JPY), and Foreign Exchange Rates [Member] | Upper Limit | Foreign currency swaps | Level 3
Unobservable Inputs
Interest rates	2.00%	[4]
Assets [Member] | Public Utilities | Level 3
Unobservable Inputs
Historical Volatility Rate	8.85%
Assets [Member] | Sovereign and Supranational | Level 3
Unobservable Inputs
Historical Volatility Rate	8.85%
Assets [Member] | Banks/financial Institutions | Level 3
Unobservable Inputs
Historical Volatility Rate	8.85%
Assets [Member] | Banks/financial Institutions | Perpetual Securities | Level 3
Unobservable Inputs
Historical Volatility Rate	8.85%
Assets [Member] | Other Corporate | Level 3
Unobservable Inputs
Historical Volatility Rate	8.85%
Assets [Member] | Lower Limit | Equity Securities | Level 3
Unobservable Inputs
Offered quotes (in dollars per share)	0
Assets [Member] | Lower Limit | Interest rate swaps | Level 3
Unobservable Inputs
Base correlation	44.00%	[1]
CDS spreads	0.03%
Recovery rate	25.00%
Assets [Member] | Upper Limit | Equity Securities | Level 3
Unobservable Inputs
Offered quotes (in dollars per share)	993
Assets [Member] | Upper Limit | Interest rate swaps | Level 3
Unobservable Inputs
Base correlation	52.00%	[1]
CDS spreads	16.73%
Recovery rate	70.00%
Assets [Member] | Weighted Average | Equity Securities | Level 3
Unobservable Inputs
Offered quotes (in dollars per share)	4
Assets [Member] | Weighted Average | Interest rate swaps | Level 3
Unobservable Inputs
CDS spreads	1.36%
Recovery rate	40.00%
Assets [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Foreign currency swaps | Level 3
Unobservable Inputs
Foreign exchange rates	20.69%	[2]
Assets [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Lower Limit | Foreign currency swaps | Level 3
Unobservable Inputs
CDS spreads	0.06%
Assets [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Upper Limit | Foreign currency swaps | Level 3
Unobservable Inputs
CDS spreads	1.57%
Assets [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), CDS Spreads and Foreign Exchange Rates [Member] | Weighted Average | Foreign currency swaps | Level 3
Unobservable Inputs
CDS spreads	1.12%
Assets [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Lower Limit | Foreign currency swaps | Level 3
Unobservable Inputs
CDS spreads	0.13%
Assets [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Upper Limit | Foreign currency swaps | Level 3
Unobservable Inputs
CDS spreads	1.90%
Assets [Member] | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Weighted Average | Foreign currency swaps | Level 3
Unobservable Inputs
CDS spreads	0.97%
Assets [Member] | Fair Value, Unobservable Input, Interest Rates (USD), interest rates (JPY), and Foreign Exchange Rates [Member] | Foreign currency swaps | Level 3
Unobservable Inputs
Foreign exchange rates	20.69%	[2]
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 | Level 3
Unobservable Inputs
Interest rates	2.29%	[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 | Level 3
Unobservable Inputs
Interest rates	3.05%	[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 | Level 3
Unobservable Inputs
Interest rates	2.29%	[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 | Level 3
Unobservable Inputs
Interest rates	3.05%	[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 | Level 3
Unobservable Inputs
Interest rates	2.29%	[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 | Level 3
Unobservable Inputs
Interest rates	3.05%	[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 | Level 3
Unobservable Inputs
Interest rates	1.04%	[4]
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 | Level 3
Unobservable Inputs
Interest rates	2.00%	[4]
Assets [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Lower Limit | Foreign currency swaps | Level 3
Unobservable Inputs
Interest rates	1.04%	[4]
Assets [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY), and CDS Spreads [Member] | Upper Limit | Foreign currency swaps | Level 3
Unobservable Inputs
Interest rates	2.00%	[4]
Assets [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), interest rates (JPY), and Foreign Exchange Rates [Member] | Lower Limit | Foreign currency swaps | Level 3
Unobservable Inputs
Interest rates	1.04%	[4]
Assets [Member] | Japan, Yen | Fair Value, Unobservable Input, Interest Rates (USD), interest rates (JPY), and Foreign Exchange Rates [Member] | Upper Limit | Foreign currency swaps | Level 3
Unobservable Inputs
Interest rates	2.00%	[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