INVESTMENTS - Total Investments in Bank and Financial Institution Sector, Including those Classified as Perpetual Securities (Detail) (Banks/financial Institutions, USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Summary of Investment Holdings [Line Items]
Amortized Cost	$ 22,907	$ 26,578
Fair Value	22,929	25,011
Percentage of Total Investment Portfolio, Amortized Cost	19.00%	27.00%
Percentage of Total Investment Portfolio, Fair Value	19.00%	25.00%
Debt Securities
Summary of Investment Holdings [Line Items]
Amortized Cost	18,424	20,025
Fair Value	18,581	18,933
Percentage of Total Investment Portfolio, Amortized Cost	15.00%	20.00%
Percentage of Total Investment Portfolio, Fair Value	15.00%	19.00%
Perpetual Securities | Upper Tier II
Summary of Investment Holdings [Line Items]
Amortized Cost	3,189	4,285
Fair Value	3,165	4,244
Percentage of Total Investment Portfolio, Amortized Cost	3.00%	5.00%
Percentage of Total Investment Portfolio, Fair Value	3.00%	4.00%
Perpetual Securities | Tier I
Summary of Investment Holdings [Line Items]
Amortized Cost	1,294	2,268
Fair Value	$ 1,183	$ 1,834
Percentage of Total Investment Portfolio, Amortized Cost	1.00%	2.00%
Percentage of Total Investment Portfolio, Fair Value	1.00%	2.00%