INVESTMENTS - Held-to-Maturity Investments in Debt Securities (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	$ 33,293	$ 34,242
Gross Unrealized Gains	3,320	4,379
Gross Unrealized Losses	248	124
Fair Value	36,365	38,497
Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost		34,242
Fair Value	36,365	38,497
Yen-denominated | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	33,293	34,242
Gross Unrealized Gains	3,320	4,379
Gross Unrealized Losses	248	124
Fair Value	36,365	38,497
Japan government and agencies | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	19,708	20,023
Fair Value	22,249	23,218
Japan government and agencies | Yen-denominated | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	19,708	20,023
Gross Unrealized Gains	2,541	3,195
Gross Unrealized Losses	0	0
Fair Value	22,249	23,218
Municipalities | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	339	346
Fair Value	397	417
Municipalities | Yen-denominated | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	339	346
Gross Unrealized Gains	58	71
Gross Unrealized Losses	0	0
Fair Value	397	417
Mortgage- and asset-backed securities | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	39	43
Fair Value	41	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	39	43
Gross Unrealized Gains	2	3
Gross Unrealized Losses	0	0
Fair Value	41	46
Public utilities | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,209	3,342
Fair Value	3,295	3,603
Public utilities | Yen-denominated | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,209	3,342
Gross Unrealized Gains	158	281
Gross Unrealized Losses	72	20
Fair Value	3,295	3,603
Sovereign and supranational | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	2,516	2,556
Fair Value	2,688	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	2,516	2,556
Gross Unrealized Gains	193	272
Gross Unrealized Losses	21	14
Fair Value	2,688	2,814
Banks/financial institutions | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	4,528	4,932
Fair Value	4,550	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	4,528	4,932
Gross Unrealized Gains	143	231
Gross Unrealized Losses	121	78
Fair Value	4,550	5,085
Other corporate | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	2,954	3,000
Fair Value	3,145	3,314
Other corporate | Yen-denominated | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	2,954	3,000
Gross Unrealized Gains	225	326
Gross Unrealized Losses	34	12
Fair Value	$ 3,145	$ 3,314