INVESTMENTS - Available-For-Sale Investments in Debt Securities, Perpetual Securities and Equity Securities (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 74,148	$ 62,963
Gross Unrealized Gains	10,745	6,627
Gross Unrealized Losses	1,094	1,796
Fair Value	83,799	67,794
Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	70,929	60,642
Gross Unrealized Gains	10,515	6,405
Gross Unrealized Losses	917	1,698
Fair Value	80,527	65,349
Perpetual securities:
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	1,950	1,841
Gross Unrealized Gains	170	200
Gross Unrealized Losses	126	94
Fair Value	1,994	1,947
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	1,269	480
Gross Unrealized Gains	60	22
Gross Unrealized Losses	51	4
Fair Value	1,278	498
Yen-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	33,189	25,592
Gross Unrealized Gains	6,462	3,067
Gross Unrealized Losses	170	148
Fair Value	39,481	28,511
Yen-denominated | Equity securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	724	472
Gross Unrealized Gains	32	19
Gross Unrealized Losses	42	4
Fair Value	714	487
Dollar-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	37,740	35,050
Gross Unrealized Gains	4,053	3,338
Gross Unrealized Losses	747	1,550
Fair Value	41,046	36,838
Dollar-denominated | Equity securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	545	8
Gross Unrealized Gains	28	3
Gross Unrealized Losses	9	0
Fair Value	564	11
Japan government and agencies | Yen-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	22,563	17,293
Gross Unrealized Gains	4,700	1,862
Gross Unrealized Losses	23	0
Fair Value	27,240	19,155
Municipalities | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,353	1,208
Municipalities | Yen-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	223	128
Gross Unrealized Gains	44	9
Gross Unrealized Losses	2	0
Fair Value	265	137
Municipalities | Dollar-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	929	926
Gross Unrealized Gains	162	151
Gross Unrealized Losses	3	6
Fair Value	1,088	1,071
Mortgage- and asset-backed securities | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,228	582
Mortgage- and asset-backed securities | Yen-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	969	322
Gross Unrealized Gains	45	33
Gross Unrealized Losses	3	0
Fair Value	1,011	355
Mortgage- and asset-backed securities | Dollar-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	202	200
Gross Unrealized Gains	15	27
Gross Unrealized Losses	0	0
Fair Value	217	227
Public utilities | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	8,509	7,479
Public utilities | Yen-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	1,667	1,400
Gross Unrealized Gains	371	210
Gross Unrealized Losses	0	10
Fair Value	2,038	1,600
Public utilities | Dollar-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	5,721	5,464
Gross Unrealized Gains	804	636
Gross Unrealized Losses	54	221
Fair Value	6,471	5,879
Sovereign and supranational | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,598	1,407
Sovereign and supranational | Yen-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	943	791
Gross Unrealized Gains	205	180
Gross Unrealized Losses	0	0
Fair Value	1,148	971
Sovereign and supranational | Dollar-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	355	331
Gross Unrealized Gains	95	105
Gross Unrealized Losses	0	0
Fair Value	450	436
Banks/financial institutions | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	6,344	6,019
Banks/financial institutions | Perpetual securities:
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,768	1,742
Banks/financial institutions | Yen-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,752	2,321
Gross Unrealized Gains	411	325
Gross Unrealized Losses	99	105
Fair Value	3,064	2,541
Banks/financial institutions | Yen-denominated | Perpetual securities:
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	1,679	1,581
Gross Unrealized Gains	138	143
Gross Unrealized Losses	126	93
Fair Value	1,691	1,631
Banks/financial institutions | Dollar-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,754	2,865
Gross Unrealized Gains	537	634
Gross Unrealized Losses	11	21
Fair Value	3,280	3,478
Banks/financial institutions | Dollar-denominated | Perpetual securities:
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	53	77
Gross Unrealized Gains	24	35
Gross Unrealized Losses	0	1
Fair Value	77	111
Other corporate | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	34,089	29,378
Other corporate | Perpetual securities:
Schedule of Available-for-sale Securities [Line Items]
Fair Value	226	205
Other corporate | Yen-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	4,072	3,337
Gross Unrealized Gains	686	448
Gross Unrealized Losses	43	33
Fair Value	4,715	3,752
Other corporate | Yen-denominated | Perpetual securities:
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	218	183
Gross Unrealized Gains	8	22
Gross Unrealized Losses	0	0
Fair Value	226	205
Other corporate | Dollar-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	27,629	25,154
Gross Unrealized Gains	2,424	1,774
Gross Unrealized Losses	679	1,302
Fair Value	29,374	25,626
U.S. government and agencies | Dollar-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	150	110
Gross Unrealized Gains	16	11
Gross Unrealized Losses	0	0
Fair Value	$ 166	$ 121