INVESTMENTS - Held-to-Maturity Investments in Debt Securities (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	$ 38,772	$ 33,459
Gross Unrealized Gains	9,220	4,278
Gross Unrealized Losses	55	217
Fair Value	47,937	37,520
Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	47,937	37,520
Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	38,772	33,459
Gross Unrealized Gains	9,220	4,278
Gross Unrealized Losses	55	217
Fair Value	47,937	37,520
Japan government and agencies | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	23,852	20,004
Gross Unrealized Gains	7,241	3,387
Gross Unrealized Losses	0	0
Fair Value	31,093	23,391
Municipalities | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	404	341
Fair Value	549	415
Municipalities | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	404	341
Gross Unrealized Gains	145	74
Gross Unrealized Losses	0	0
Fair Value	549	415
Mortgage- and asset-backed securities | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	37	36
Fair Value	39	38
Mortgage- and asset-backed securities | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	37	36
Gross Unrealized Gains	2	2
Gross Unrealized Losses	0	0
Fair Value	39	38
Public utilities | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,687	3,092
Fair Value	4,198	3,203
Public utilities | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,687	3,092
Gross Unrealized Gains	525	205
Gross Unrealized Losses	14	94
Fair Value	4,198	3,203
Sovereign and supranational | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	2,998	2,555
Fair Value	3,394	2,711
Sovereign and supranational | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	2,998	2,555
Gross Unrealized Gains	402	182
Gross Unrealized Losses	6	26
Fair Value	3,394	2,711
Banks/financial institutions | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	4,544	4,431
Fair Value	4,790	4,546
Banks/financial institutions | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	4,544	4,431
Gross Unrealized Gains	271	168
Gross Unrealized Losses	25	53
Fair Value	4,790	4,546
Other corporate | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,250	3,000
Fair Value	3,874	3,216
Other corporate | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,250	3,000
Gross Unrealized Gains	634	260
Gross Unrealized Losses	10	44
Fair Value	$ 3,874	$ 3,216