INVESTMENTS - Available-For-Sale Investments in Debt Securities, Perpetual Securities and Equity Securities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 57,646	$ 52,275
Gross Unrealized Gains	4,716	3,679
Gross Unrealized Losses	784	1,918
Fair Value	61,578	54,036
Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	53,413	45,356
Gross Unrealized Gains	4,453	3,500
Gross Unrealized Losses	613	1,284
Fair Value	57,253	47,572
Perpetual securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	4,213	6,897
Gross Unrealized Gains	259	175
Gross Unrealized Losses	170	633
Fair Value	4,302	6,439
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	20	22
Gross Unrealized Gains	4	4
Gross Unrealized Losses	1	1
Fair Value	23	25
Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	27,481	28,099
Gross Unrealized Gains	1,050	1,053
Gross Unrealized Losses	487	1,061
Fair Value	28,044	28,091
Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	25,932	17,257
Gross Unrealized Gains	3,403	2,447
Gross Unrealized Losses	126	223
Fair Value	29,209	19,481
Japan government and agencies | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	12,612	11,108
Gross Unrealized Gains	349	670
Gross Unrealized Losses	81	0
Fair Value	12,880	11,778
Mortgage- and asset-backed Securities | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	746	912
Gross Unrealized Gains	40	43
Gross Unrealized Losses	1	1
Fair Value	785	954
Mortgage- and asset-backed Securities | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	188	310
Gross Unrealized Gains	58	74
Gross Unrealized Losses	0	0
Fair Value	246	384
Public Utilities | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	3,608	3,850
Gross Unrealized Gains	116	59
Gross Unrealized Losses	72	226
Fair Value	3,652	3,683
Public Utilities | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	4,204	3,052
Gross Unrealized Gains	658	517
Gross Unrealized Losses	17	27
Fair Value	4,845	3,542
Sovereign and Supranational | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	1,404	1,704
Gross Unrealized Gains	71	87
Gross Unrealized Losses	0	16
Fair Value	1,475	1,775
Sovereign and Supranational | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	476	449
Gross Unrealized Gains	123	89
Gross Unrealized Losses	2	5
Fair Value	597	533
Banks/financial Institutions | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	3,455	4,312
Gross Unrealized Gains	233	74
Gross Unrealized Losses	180	359
Fair Value	3,508	4,027
Banks/financial Institutions | Yen Denominated | Perpetual securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	3,635	6,217
Gross Unrealized Gains	193	155
Gross Unrealized Losses	161	604
Fair Value	3,667	5,768
Banks/financial Institutions | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	3,626	3,324
Gross Unrealized Gains	506	223
Gross Unrealized Losses	6	121
Fair Value	4,126	3,426
Banks/financial Institutions | Dollar Denominated | Perpetual securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	269	336
Gross Unrealized Gains	23	3
Gross Unrealized Losses	9	29
Fair Value	283	310
Other Corporate | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	5,656	6,213
Gross Unrealized Gains	241	120
Gross Unrealized Losses	153	459
Fair Value	5,744	5,874
Other Corporate | Yen Denominated | Perpetual securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	309	344
Gross Unrealized Gains	43	17
Gross Unrealized Losses	0	0
Fair Value	352	361
Other Corporate | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	16,300	9,031
Gross Unrealized Gains	1,878	1,433
Gross Unrealized Losses	95	62
Fair Value	18,083	10,402
U.S. Government and Agencies | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	93	31
Gross Unrealized Gains	24	4
Gross Unrealized Losses	0	0
Fair Value	117	35
Municipalities | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	1,045	1,060
Gross Unrealized Gains	156	107
Gross Unrealized Losses	6	8
Fair Value	$ 1,195	$ 1,159