INVESTMENTS - Available-For-Sale Investments in Debt Securities, Perpetual Securities and Equity Securities (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 54,536	$ 54,036
Cost or Amortized Cost	52,264	52,275
Gross Unrealized Gains	4,084	3,679
Gross Unrealized Losses	1,812	1,918
Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	49,781	47,572
Cost or Amortized Cost	46,961	45,356
Gross Unrealized Gains	4,042	3,500
Gross Unrealized Losses	1,222	1,284
Perpetual Securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	4,732	6,439
Cost or Amortized Cost	5,282	6,897
Gross Unrealized Gains	38	175
Gross Unrealized Losses	588	633
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	23	25
Cost or Amortized Cost	21	22
Gross Unrealized Gains	4	4
Gross Unrealized Losses	2	1
Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	29,040	28,091
Cost or Amortized Cost	28,918	28,099
Gross Unrealized Gains	1,225	1,053
Gross Unrealized Losses	1,103	1,061
Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	20,741	19,481
Cost or Amortized Cost	18,043	17,257
Gross Unrealized Gains	2,817	2,447
Gross Unrealized Losses	119	223
Japan government and agencies | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	12,418	11,778
Cost or Amortized Cost	11,678	11,108
Gross Unrealized Gains	741	670
Gross Unrealized Losses	1	0
Mortgage- and asset-backed Securities | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	898	954
Cost or Amortized Cost	852	912
Gross Unrealized Gains	47	43
Gross Unrealized Losses	1	1
Mortgage- and asset-backed Securities | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	375	384
Cost or Amortized Cost	296	310
Gross Unrealized Gains	80	74
Gross Unrealized Losses	1	0
Public Utilities | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	3,779	3,683
Cost or Amortized Cost	3,939	3,850
Gross Unrealized Gains	73	59
Gross Unrealized Losses	233	226
Public Utilities | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	3,795	3,542
Cost or Amortized Cost	3,251	3,052
Gross Unrealized Gains	572	517
Gross Unrealized Losses	28	27
Sovereign and Supranational | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,987	1,775
Cost or Amortized Cost	2,006	1,704
Gross Unrealized Gains	46	87
Gross Unrealized Losses	65	16
Sovereign and Supranational | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	573	533
Cost or Amortized Cost	473	449
Gross Unrealized Gains	103	89
Gross Unrealized Losses	3	5
Banks/financial Institutions | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	3,967	4,027
Cost or Amortized Cost	4,226	4,312
Gross Unrealized Gains	177	74
Gross Unrealized Losses	436	359
Banks/financial Institutions | Yen Denominated | Perpetual Securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	4,091	5,768
Cost or Amortized Cost	4,634	6,217
Gross Unrealized Gains	27	155
Gross Unrealized Losses	570	604
Banks/financial Institutions | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	3,749	3,426
Cost or Amortized Cost	3,449	3,324
Gross Unrealized Gains	341	223
Gross Unrealized Losses	41	121
Banks/financial Institutions | Dollar Denominated | Perpetual Securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	299	310
Cost or Amortized Cost	310	336
Gross Unrealized Gains	7	3
Gross Unrealized Losses	18	29
Other Corporate | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	5,991	5,874
Cost or Amortized Cost	6,217	6,213
Gross Unrealized Gains	141	120
Gross Unrealized Losses	367	459
Other Corporate | Yen Denominated | Perpetual Securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	342	361
Cost or Amortized Cost	338	344
Gross Unrealized Gains	4	17
Gross Unrealized Losses	0	0
Other Corporate | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	10,944	10,402
Cost or Amortized Cost	9,428	9,031
Gross Unrealized Gains	1,555	1,433
Gross Unrealized Losses	39	62
U.S. Government and Agencies | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	116	35
Cost or Amortized Cost	94	31
Gross Unrealized Gains	22	4
Gross Unrealized Losses	0	0
Municipalities | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,189	1,159
Cost or Amortized Cost	1,052	1,060
Gross Unrealized Gains	144	107
Gross Unrealized Losses	$ 7	$ 8