INVESTMENTS - Available-For-Sale Investments in Debt Securities, Perpetual Securities and Equity Securities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 60,844	$ 59,515
Gross Unrealized Gains	8,136	3,659
Gross Unrealized Losses	710	2,136
Fair Value	68,270	61,038
Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	58,385	56,511
Gross Unrealized Gains	7,806	3,468
Gross Unrealized Losses	618	1,909
Fair Value	65,573	58,070
Perpetual securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,440	2,987
Gross Unrealized Gains	321	186
Gross Unrealized Losses	92	226
Fair Value	2,669	2,947
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	19	17
Gross Unrealized Gains	9	5
Gross Unrealized Losses	0	1
Fair Value	28	21
Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	26,501	25,488
Gross Unrealized Gains	3,029	1,016
Gross Unrealized Losses	242	506
Fair Value	29,288	25,998
Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	31,884	31,023
Gross Unrealized Gains	4,777	2,452
Gross Unrealized Losses	376	1,403
Fair Value	36,285	32,072
Japan government and agencies | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	17,341	14,936
Gross Unrealized Gains	1,740	431
Gross Unrealized Losses	0	33
Fair Value	19,081	15,334
Mortgage- and asset-backed securities | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	602	771
Mortgage- and asset-backed securities | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	351	558
Gross Unrealized Gains	35	29
Gross Unrealized Losses	0	0
Fair Value	386	587
Mortgage- and asset-backed securities | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	185	163
Gross Unrealized Gains	31	21
Gross Unrealized Losses	0	0
Fair Value	216	184
Public utilities | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	7,897	7,562
Public utilities | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	1,691	2,261
Gross Unrealized Gains	226	100
Gross Unrealized Losses	5	18
Fair Value	1,912	2,343
Public utilities | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	5,061	4,931
Gross Unrealized Gains	960	471
Gross Unrealized Losses	36	183
Fair Value	5,985	5,219
Sovereign and supranational | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,416	1,523
Sovereign and supranational | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	799	978
Gross Unrealized Gains	163	85
Gross Unrealized Losses	0	28
Fair Value	962	1,035
Sovereign and supranational | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	343	404
Gross Unrealized Gains	111	85
Gross Unrealized Losses	0	1
Fair Value	454	488
Banks/financial Institutions | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	6,598	6,509
Banks/financial Institutions | Perpetual securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	2,438	2,738
Banks/financial Institutions | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,752	2,799
Gross Unrealized Gains	325	220
Gross Unrealized Losses	189	242
Fair Value	2,888	2,777
Banks/financial Institutions | Yen-denominated | Perpetual securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,132	2,582
Gross Unrealized Gains	223	151
Gross Unrealized Losses	92	217
Fair Value	2,263	2,516
Banks/financial Institutions | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,943	3,318
Gross Unrealized Gains	775	447
Gross Unrealized Losses	8	33
Fair Value	3,710	3,732
Banks/financial Institutions | Dollar-denominated | Perpetual securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	125	196
Gross Unrealized Gains	50	35
Gross Unrealized Losses	0	9
Fair Value	175	222
Other corporate | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	28,605	25,222
Other corporate | Perpetual securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	231	209
Other corporate | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	3,479	3,956
Gross Unrealized Gains	531	151
Gross Unrealized Losses	48	185
Fair Value	3,962	3,922
Other corporate | Yen-denominated | Perpetual securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	183	209
Gross Unrealized Gains	48	0
Gross Unrealized Losses	0	0
Fair Value	231	209
Other corporate | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	22,291	21,123
Gross Unrealized Gains	2,682	1,347
Gross Unrealized Losses	330	1,170
Fair Value	24,643	21,300
U.S. Government and Agencies | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	100	92
Gross Unrealized Gains	17	10
Gross Unrealized Losses	0	4
Fair Value	117	98
Municipalities | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,257	1,051
Municipalities | Yen-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	88
Gross Unrealized Gains	9
Gross Unrealized Losses	0
Fair Value	97
Municipalities | Dollar-denominated | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	961	992
Gross Unrealized Gains	201	71
Gross Unrealized Losses	2	12
Fair Value	$ 1,160	$ 1,051