INVESTMENTS - Available-For-Sale Investments in Debt Securities, Perpetual Securities and Equity Securities (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 61,242	$ 60,844
Gross Unrealized Gains	6,702	8,136
Gross Unrealized Losses	1,259	710
Fair Value	66,685	68,270
Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	59,130	58,385
Gross Unrealized Gains	6,461	7,806
Gross Unrealized Losses	1,149	618
Fair Value	64,442	65,573
Perpetual securities:
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,093	2,440
Gross Unrealized Gains	231	321
Gross Unrealized Losses	110	92
Fair Value	2,214	2,669
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	19	19
Gross Unrealized Gains	10	9
Gross Unrealized Losses	0	0
Fair Value	29	28
Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	25,018	26,501
Gross Unrealized Gains	2,493	3,029
Gross Unrealized Losses	219	242
Fair Value	27,292	29,288
Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	34,112	31,884
Gross Unrealized Gains	3,968	4,777
Gross Unrealized Losses	930	376
Fair Value	37,150	36,285
Japan government and agencies | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	16,315	17,341
Gross Unrealized Gains	1,289	1,740
Gross Unrealized Losses	6	0
Fair Value	17,598	19,081
Municipalities | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,155	1,257
Municipalities | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	86	88
Gross Unrealized Gains	5	9
Gross Unrealized Losses	0	0
Fair Value	91	97
Municipalities | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	924	961
Gross Unrealized Gains	150	201
Gross Unrealized Losses	10	2
Fair Value	1,064	1,160
Mortgage- and asset-backed securities | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	597	602
Mortgage- and asset-backed securities | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	329	351
Gross Unrealized Gains	29	35
Gross Unrealized Losses	0	0
Fair Value	358	386
Mortgage- and asset-backed securities | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	209	185
Gross Unrealized Gains	30	31
Gross Unrealized Losses	0	0
Fair Value	239	216
Public utilities | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	7,776	7,897
Public utilities | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	1,581	1,691
Gross Unrealized Gains	225	226
Gross Unrealized Losses	3	5
Fair Value	1,803	1,912
Public utilities | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	5,331	5,061
Gross Unrealized Gains	760	960
Gross Unrealized Losses	118	36
Fair Value	5,973	5,985
Sovereign and supranational | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,437	1,416
Sovereign and supranational | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	779	799
Gross Unrealized Gains	210	163
Gross Unrealized Losses	0	0
Fair Value	989	962
Sovereign and supranational | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	338	343
Gross Unrealized Gains	110	111
Gross Unrealized Losses	0	0
Fair Value	448	454
Banks/financial institutions | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	6,389	6,598
Banks/financial institutions | Perpetual securities:
Schedule of Available-for-sale Securities [Line Items]
Fair Value	2,011	2,438
Banks/financial institutions | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,642	2,752
Gross Unrealized Gains	282	325
Gross Unrealized Losses	184	189
Fair Value	2,740	2,888
Banks/financial institutions | Yen-denominated | Perpetual securities:
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	1,802	2,132
Gross Unrealized Gains	156	223
Gross Unrealized Losses	110	92
Fair Value	1,848	2,263
Banks/financial institutions | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,954	2,943
Gross Unrealized Gains	715	775
Gross Unrealized Losses	20	8
Fair Value	3,649	3,710
Banks/financial institutions | Dollar-denominated | Perpetual securities:
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	111	125
Gross Unrealized Gains	52	50
Gross Unrealized Losses	0	0
Fair Value	163	175
Other corporate | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	29,371	28,605
Other corporate | Perpetual securities:
Schedule of Available-for-sale Securities [Line Items]
Fair Value	203	231
Other corporate | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	3,286	3,479
Gross Unrealized Gains	453	531
Gross Unrealized Losses	26	48
Fair Value	3,713	3,962
Other corporate | Yen-denominated | Perpetual securities:
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	180	183
Gross Unrealized Gains	23	48
Gross Unrealized Losses	0	0
Fair Value	203	231
Other corporate | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	24,248	22,291
Gross Unrealized Gains	2,192	2,682
Gross Unrealized Losses	782	330
Fair Value	25,658	24,643
U.S. government and agencies | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	108	100
Gross Unrealized Gains	11	17
Gross Unrealized Losses	0	0
Fair Value	$ 119	$ 117