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	Mar. 31, 2012	Dec. 31, 2011
Summary of Investment Holdings [Line Items]
Amortized Cost	$ 24,328	$ 26,578
Fair Value	23,588	25,011
Percentage of Total Investment Portfolio, Amortized Cost	24.00%	27.00%
Percentage of Total Investment Portfolio, Fair Value	24.00%	25.00%
Debt Securities
Summary of Investment Holdings [Line Items]
Amortized Cost	19,132	20,025
Fair Value	18,587	18,933
Percentage of Total Investment Portfolio, Amortized Cost	19.00%	20.00%
Percentage of Total Investment Portfolio, Fair Value	19.00%	19.00%
Perpetual Securities | Upper Tier II
Summary of Investment Holdings [Line Items]
Amortized Cost	3,251	4,285
Fair Value	3,193	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	1,945	2,268
Fair Value	$ 1,808	$ 1,834
Percentage of Total Investment Portfolio, Amortized Cost	2.00%	2.00%
Percentage of Total Investment Portfolio, Fair Value	2.00%	2.00%