INVESTMENTS - Held-to-Maturity Investments in Debt Securities (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	$ 33,729	$ 34,242
Gross Unrealized Gains	3,589	4,379
Gross Unrealized Losses	370	124
Fair Value	36,948	38,497
Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost		34,242
Fair Value	36,948	38,497
Yen-denominated | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	33,729	34,242
Gross Unrealized Gains	3,589	4,379
Gross Unrealized Losses	370	124
Fair Value	36,948	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	20,115	20,023
Gross Unrealized Gains	2,876	3,195
Gross Unrealized Losses	0	0
Fair Value	22,991	23,218
Municipalities | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	345	346
Fair Value	409	417
Municipalities | Yen-denominated | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	345	346
Gross Unrealized Gains	64	71
Gross Unrealized Losses	0	0
Fair Value	409	417
Mortgage- and asset-backed securities | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	38	43
Fair Value	40	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	38	43
Gross Unrealized Gains	2	3
Gross Unrealized Losses	0	0
Fair Value	40	46
Public utilities | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,108	3,342
Fair Value	3,128	3,603
Public utilities | Yen-denominated | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,108	3,342
Gross Unrealized Gains	151	281
Gross Unrealized Losses	131	20
Fair Value	3,128	3,603
Sovereign and supranational | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	2,569	2,556
Fair Value	2,686	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	2,569	2,556
Gross Unrealized Gains	164	272
Gross Unrealized Losses	47	14
Fair Value	2,686	2,814
Banks/financial institutions | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	4,539	4,932
Fair Value	4,544	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	4,539	4,932
Gross Unrealized Gains	141	231
Gross Unrealized Losses	136	78
Fair Value	4,544	5,085
Other corporate | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,015	3,000
Fair Value	3,150	3,314
Other corporate | Yen-denominated | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,015	3,000
Gross Unrealized Gains	191	326
Gross Unrealized Losses	56	12
Fair Value	$ 3,150	$ 3,314