INVESTMENTS - Available-For-Sale Investments in Debt Securities, Perpetual Securities and Equity Securities (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 57,500	$ 52,275
Gross Unrealized Gains	4,737	3,679
Gross Unrealized Losses	1,246	1,918
Fair Value	60,991	54,036
Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	52,650	45,356
Gross Unrealized Gains	4,549	3,500
Gross Unrealized Losses	951	1,284
Fair Value	56,248	47,572
Perpetual Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	4,828	6,897
Gross Unrealized Gains	184	175
Gross Unrealized Losses	293	633
Fair Value	4,719	6,439
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	22	22
Gross Unrealized Gains	4	4
Gross Unrealized Losses	2	1
Fair Value	24	25
Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	31,768	28,099
Gross Unrealized Gains	1,107	1,053
Gross Unrealized Losses	883	1,061
Fair Value	31,992	28,091
Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	20,882	17,257
Gross Unrealized Gains	3,442	2,447
Gross Unrealized Losses	68	223
Fair Value	24,256	19,481
Japan government and agencies | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	14,059	11,108
Gross Unrealized Gains	488	670
Gross Unrealized Losses	6	0
Fair Value	14,541	11,778
Mortgage- and asset-backed Securities | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	853	912
Gross Unrealized Gains	51	43
Gross Unrealized Losses	1	1
Fair Value	903	954
Mortgage- and asset-backed Securities | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	235	310
Gross Unrealized Gains	67	74
Gross Unrealized Losses	0	0
Fair Value	302	384
Public Utilities | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	4,026	3,850
Gross Unrealized Gains	107	59
Gross Unrealized Losses	142	226
Fair Value	3,991	3,683
Public Utilities | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	3,620	3,052
Gross Unrealized Gains	699	517
Gross Unrealized Losses	3	27
Fair Value	4,316	3,542
Sovereign and Supranational | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,050	1,704
Gross Unrealized Gains	53	87
Gross Unrealized Losses	109	16
Fair Value	1,994	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	121	89
Gross Unrealized Losses	4	5
Fair Value	593	533
Banks/financial Institutions | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	4,473	4,312
Gross Unrealized Gains	194	74
Gross Unrealized Losses	369	359
Fair Value	4,298	4,027
Banks/financial Institutions | Yen Denominated | Perpetual Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	4,214	6,217
Gross Unrealized Gains	139	155
Gross Unrealized Losses	281	604
Fair Value	4,072	5,768
Banks/financial Institutions | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	3,526	3,324
Gross Unrealized Gains	476	223
Gross Unrealized Losses	17	121
Fair Value	3,985	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	19	3
Gross Unrealized Losses	12	29
Fair Value	276	310
Other Corporate | Yen Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	6,307	6,213
Gross Unrealized Gains	214	120
Gross Unrealized Losses	256	459
Fair Value	6,265	5,874
Other Corporate | Yen Denominated | Perpetual Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	345	344
Gross Unrealized Gains	26	17
Gross Unrealized Losses	0	0
Fair Value	371	361
Other Corporate | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	11,883	9,031
Gross Unrealized Gains	1,902	1,433
Gross Unrealized Losses	39	62
Fair Value	13,746	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	25	4
Gross Unrealized Losses	0	0
Fair Value	118	35
Municipalities | Dollar Denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	1,049	1,060
Gross Unrealized Gains	152	107
Gross Unrealized Losses	5	8
Fair Value	$ 1,196	$ 1,159