INVESTMENTS - Held-to-Maturity Investments in Debt Securities (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	$ 33,459	$ 34,242
Gross Unrealized Gains	4,278	4,379
Gross Unrealized Losses	217	124
Fair Value	37,520	38,497
Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	37,520	38,497
Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	33,459
Gross Unrealized Gains	4,278	4,379
Gross Unrealized Losses	217	124
Fair Value	37,520	38,497
Japan government and agencies | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	20,004
Gross Unrealized Gains	3,387	3,195
Gross Unrealized Losses	0	0
Fair Value	23,391	23,218
Municipalities | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	341	346
Fair Value	415	417
Municipalities | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	341
Gross Unrealized Gains	74	71
Gross Unrealized Losses	0	0
Fair Value	415	417
Mortgage- and asset-backed securities | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	36	43
Fair Value	38	46
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	36
Gross Unrealized Gains	2	3
Gross Unrealized Losses	0	0
Fair Value	38	46
Public utilities | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,092	3,342
Fair Value	3,203	3,603
Public utilities | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,092
Gross Unrealized Gains	205	281
Gross Unrealized Losses	94	20
Fair Value	3,203	3,603
Sovereign and supranational | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	2,555	2,556
Fair Value	2,711	2,814
Sovereign and supranational | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	2,555
Gross Unrealized Gains	182	272
Gross Unrealized Losses	26	14
Fair Value	2,711	2,814
Banks/financial institutions | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	4,431	4,932
Fair Value	4,546	5,085
Banks/financial institutions | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	4,431
Gross Unrealized Gains	168	231
Gross Unrealized Losses	53	78
Fair Value	4,546	5,085
Other corporate | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,000	3,000
Fair Value	3,216	3,314
Other corporate | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,000
Gross Unrealized Gains	260	326
Gross Unrealized Losses	44	12
Fair Value	$ 3,216	$ 3,314