FAIR VALUE MEASUREMENTS - Fair Value Hierarchy Levels of Assets and Liabilities Carried at Cost or Amortized Cost (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Assets:
Cost or Amortized Cost	$ 42,718	$ 54,426
Securities held to maturity, fixed maturities, fair value	42,761	54,841
Liabilities:
Other policyholders' funds	5,018	5,319
Other policyholders' funds fair value disclosure	4,873	5,151
Notes Payable	4,939	4,343
Notes payable (excluding capital leases), fair value	5,369	4,992
Obligation To Japanese Policyholder Protection Corporation Carrying Value	2	23
Obligation to Japanese Policyholder Protection Corporation Fair Value Disclosure	2	23
Total Financial Instrument Liabilities Not Carried At Fair Value	9,959	9,685
Liabilities Fair Value Disclosure Financial Instruments Carried At Cost	10,244	10,166
Fixed Maturities
Assets:
Cost or Amortized Cost	42,718	54,426
Securities held to maturity, fixed maturities, fair value	42,761	54,841
Japan government and agencies | Fixed Maturities
Assets:
Cost or Amortized Cost	23,946	32,043
Securities held to maturity, fixed maturities, fair value	24,682	32,332
Municipalities | Fixed Maturities
Assets:
Cost or Amortized Cost	429	492
Securities held to maturity, fixed maturities, fair value	467	520
Mortgage- and asset-backed Securities | Fixed Maturities
Assets:
Cost or Amortized Cost	67	90
Securities held to maturity, fixed maturities, fair value	70	94
Public Utilities | Fixed Maturities
Assets:
Cost or Amortized Cost	4,323	4,924
Securities held to maturity, fixed maturities, fair value	4,192	5,051
Sovereign and Supranational | Fixed Maturities
Assets:
Cost or Amortized Cost	2,817	3,209
Securities held to maturity, fixed maturities, fair value	2,844	3,317
Banks/financial Institutions | Fixed Maturities
Assets:
Cost or Amortized Cost	7,222	9,211
Securities held to maturity, fixed maturities, fair value	6,632	8,991
Other Corporate | Fixed Maturities
Assets:
Cost or Amortized Cost	3,914	4,457
Securities held to maturity, fixed maturities, fair value	3,874	4,536
Level 1
Liabilities:
Other policyholders' funds fair value disclosure	0	0
Notes payable (excluding capital leases), fair value	0	0
Obligation to Japanese Policyholder Protection Corporation Fair Value Disclosure	0	0
Liabilities Fair Value Disclosure Financial Instruments Carried At Cost	0	0
Level 1 | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	24,682	32,332
Level 1 | Japan government and agencies | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	24,682	32,332
Level 1 | Municipalities | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	0	0
Level 1 | Mortgage- and asset-backed Securities | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	0	0
Level 1 | Public Utilities | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	0	0
Level 1 | Sovereign and Supranational | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	0	0
Level 1 | Banks/financial Institutions | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	0	0
Level 1 | Other Corporate | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	0	0
Level 2
Liabilities:
Other policyholders' funds fair value disclosure	0	0
Notes payable (excluding capital leases), fair value	0	0
Obligation to Japanese Policyholder Protection Corporation Fair Value Disclosure	0	0
Liabilities Fair Value Disclosure Financial Instruments Carried At Cost	0	0
Level 2 | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	18,033	22,445
Level 2 | Japan government and agencies | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	0	0
Level 2 | Municipalities | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	467	520
Level 2 | Mortgage- and asset-backed Securities | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	24	30
Level 2 | Public Utilities | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	4,192	5,051
Level 2 | Sovereign and Supranational | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	2,844	3,317
Level 2 | Banks/financial Institutions | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	6,632	8,991
Level 2 | Other Corporate | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	3,874	4,536
Level 3
Liabilities:
Other policyholders' funds fair value disclosure	4,873	5,151
Notes payable (excluding capital leases), fair value	5,369	4,992
Obligation to Japanese Policyholder Protection Corporation Fair Value Disclosure	2	23
Liabilities Fair Value Disclosure Financial Instruments Carried At Cost	10,244	10,166
Level 3 | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	46	64
Level 3 | Japan government and agencies | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	0	0
Level 3 | Municipalities | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	0	0
Level 3 | Mortgage- and asset-backed Securities | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	46	64
Level 3 | Public Utilities | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	0	0
Level 3 | Sovereign and Supranational | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	0	0
Level 3 | Banks/financial Institutions | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	0	0
Level 3 | Other Corporate | Fixed Maturities
Assets:
Securities held to maturity, fixed maturities, fair value	$ 0	$ 0