INVESTMENTS - Available-For-Sale Investments in Debt Securities, Perpetual Securities and Equity Securities (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 62,222	$ 60,844
Gross Unrealized Gains	6,637	8,136
Gross Unrealized Losses	1,456	710
Fair Value	67,403	68,270
Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	60,014	58,385
Gross Unrealized Gains	6,407	7,806
Gross Unrealized Losses	1,315	618
Fair Value	65,106	65,573
Perpetual securities:
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,089	2,440
Gross Unrealized Gains	218	321
Gross Unrealized Losses	141	92
Fair Value	2,166	2,669
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	119	19
Gross Unrealized Gains	12	9
Gross Unrealized Losses	0	0
Fair Value	131	28
Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	25,442	26,501
Gross Unrealized Gains	2,638	3,029
Gross Unrealized Losses	168	242
Fair Value	27,912	29,288
Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	34,572	31,884
Gross Unrealized Gains	3,769	4,777
Gross Unrealized Losses	1,147	376
Fair Value	37,194	36,285
Japan government and agencies | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	16,799	17,341
Gross Unrealized Gains	1,544	1,740
Gross Unrealized Losses	1	0
Fair Value	18,342	19,081
Municipalities | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,166	1,257
Municipalities | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	88	88
Gross Unrealized Gains	6	9
Gross Unrealized Losses	0	0
Fair Value	94	97
Municipalities | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	927	961
Gross Unrealized Gains	154	201
Gross Unrealized Losses	9	2
Fair Value	1,072	1,160
Mortgage- and asset-backed securities | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	591	602
Mortgage- and asset-backed securities | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	330	351
Gross Unrealized Gains	31	35
Gross Unrealized Losses	0	0
Fair Value	361	386
Mortgage- and asset-backed securities | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	201	185
Gross Unrealized Gains	29	31
Gross Unrealized Losses	0	0
Fair Value	230	216
Public utilities | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	7,848	7,897
Public utilities | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	1,613	1,691
Gross Unrealized Gains	202	226
Gross Unrealized Losses	17	5
Fair Value	1,798	1,912
Public utilities | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	5,437	5,061
Gross Unrealized Gains	742	960
Gross Unrealized Losses	129	36
Fair Value	6,050	5,985
Sovereign and supranational | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,421	1,416
Sovereign and supranational | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	795	799
Gross Unrealized Gains	185	163
Gross Unrealized Losses	0	0
Fair Value	980	962
Sovereign and supranational | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	332	343
Gross Unrealized Gains	109	111
Gross Unrealized Losses	0	0
Fair Value	441	454
Banks/financial institutions | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	6,261	6,598
Banks/financial institutions | Perpetual securities:
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,964	2,438
Banks/financial institutions | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,463	2,752
Gross Unrealized Gains	271	325
Gross Unrealized Losses	118	189
Fair Value	2,616	2,888
Banks/financial institutions | Yen-denominated | Perpetual securities:
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	1,798	2,132
Gross Unrealized Gains	149	223
Gross Unrealized Losses	140	92
Fair Value	1,807	2,263
Banks/financial institutions | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,952	2,943
Gross Unrealized Gains	707	775
Gross Unrealized Losses	14	8
Fair Value	3,645	3,710
Banks/financial institutions | Dollar-denominated | Perpetual securities:
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	107	125
Gross Unrealized Gains	51	50
Gross Unrealized Losses	1	0
Fair Value	157	175
Other corporate | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	29,354	28,605
Other corporate | Perpetual securities:
Schedule of Available-for-sale Securities [Line Items]
Fair Value	202	231
Other corporate | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	3,354	3,479
Gross Unrealized Gains	399	531
Gross Unrealized Losses	32	48
Fair Value	3,721	3,962
Other corporate | Yen-denominated | Perpetual securities:
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	184	183
Gross Unrealized Gains	18	48
Gross Unrealized Losses	0	0
Fair Value	202	231
Other corporate | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	24,612	22,291
Gross Unrealized Gains	2,016	2,682
Gross Unrealized Losses	995	330
Fair Value	25,633	24,643
U.S. government and agencies | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	111	100
Gross Unrealized Gains	12	17
Gross Unrealized Losses	0	0
Fair Value	$ 123	$ 117