INVESTMENTS - Available-For-Sale Investments in Debt Securities, Perpetual Securities and Equity Securities (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 56,430	$ 57,646
Gross Unrealized Gains	4,472	4,716
Gross Unrealized Losses	1,469	784
Fair Value	59,433	61,578
Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	52,779	53,413
Gross Unrealized Gains	4,368	4,453
Gross Unrealized Losses	871	613
Fair Value	56,276	57,253
Perpetual Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	3,633	4,213
Gross Unrealized Gains	98	259
Gross Unrealized Losses	598	170
Fair Value	3,133	4,302
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	18	20
Gross Unrealized Gains	6	4
Gross Unrealized Losses	0	1
Fair Value	24	23
Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	24,598	27,481
Gross Unrealized Gains	1,341	1,050
Gross Unrealized Losses	553	487
Fair Value	25,386	28,044
Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	28,181	25,932
Gross Unrealized Gains	3,027	3,403
Gross Unrealized Losses	318	126
Fair Value	30,890	29,209
Japan government and agencies | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	12,035	12,612
Gross Unrealized Gains	748	349
Gross Unrealized Losses	0	81
Fair Value	12,783	12,880
Mortgage- and asset-backed Securities | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	671	746
Gross Unrealized Gains	44	40
Gross Unrealized Losses	1	1
Fair Value	714	785
Mortgage- and asset-backed Securities | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	182	188
Gross Unrealized Gains	58	58
Gross Unrealized Losses	0	0
Fair Value	240	246
Public Utilities | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,928	3,608
Gross Unrealized Gains	116	116
Gross Unrealized Losses	53	72
Fair Value	2,991	3,652
Public Utilities | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	4,581	4,204
Gross Unrealized Gains	609	658
Gross Unrealized Losses	31	17
Fair Value	5,159	4,845
Sovereign and Supranational | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	1,120	1,404
Gross Unrealized Gains	61	71
Gross Unrealized Losses	7	0
Fair Value	1,174	1,475
Sovereign and Supranational | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	468	476
Gross Unrealized Gains	112	123
Gross Unrealized Losses	2	2
Fair Value	578	597
Banks/financial Institutions | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,952	3,455
Gross Unrealized Gains	183	233
Gross Unrealized Losses	236	180
Fair Value	2,899	3,508
Banks/financial Institutions | Yen Denominated | Perpetual Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	3,080	3,635
Gross Unrealized Gains	73	193
Gross Unrealized Losses	525	161
Fair Value	2,628	3,667
Banks/financial Institutions | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	3,578	3,626
Gross Unrealized Gains	502	506
Gross Unrealized Losses	8	6
Fair Value	4,072	4,126
Banks/financial Institutions | Dollar Denominated | Perpetual Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	268	269
Gross Unrealized Gains	25	23
Gross Unrealized Losses	6	9
Fair Value	287	283
Other Corporate | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	4,892	5,656
Gross Unrealized Gains	189	241
Gross Unrealized Losses	256	153
Fair Value	4,825	5,744
Other Corporate | Yen Denominated | Perpetual Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	285	309
Gross Unrealized Gains	0	43
Gross Unrealized Losses	67	0
Fair Value	218	352
Other Corporate | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	18,259	16,300
Gross Unrealized Gains	1,581	1,878
Gross Unrealized Losses	271	95
Fair Value	19,569	18,083
U.S. Government and Agencies | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	95	93
Gross Unrealized Gains	16	24
Gross Unrealized Losses	0	0
Fair Value	111	117
Municipalities | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	1,018	1,045
Gross Unrealized Gains	149	156
Gross Unrealized Losses	6	6
Fair Value	$ 1,161	$ 1,195