INVESTMENTS - Held-to-Maturity Investments in Debt Securities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Held-to-maturity Securities [Line Items]
Gross Unrealized Gains	$ 1,213
Gross Unrealized Losses	798	1,618
Fair Value	54,841	46,383
Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Cost or Amortized Cost	54,426
Yen Denominated
Schedule of Held-to-maturity Securities [Line Items]
Cost or Amortized Cost	54,426	47,009
Gross Unrealized Gains		992
Yen Denominated | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Cost or Amortized Cost		47,009
Gross Unrealized Gains	1,213	992
Gross Unrealized Losses	798	1,618
Fair Value	54,841	46,383
Japan government and agencies | Yen Denominated | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Cost or Amortized Cost		18,775
Gross Unrealized Gains	356	297
Gross Unrealized Losses	67	1
Fair Value	32,332	19,071
Municipalities | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Cost or Amortized Cost	492
Municipalities | Yen Denominated | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Cost or Amortized Cost		553
Gross Unrealized Gains	30	35
Gross Unrealized Losses	2	4
Fair Value	520	584
Mortgage- and asset-backed Securities | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Cost or Amortized Cost	90
Mortgage- and asset-backed Securities | Yen Denominated | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Cost or Amortized Cost		129
Gross Unrealized Gains	4	5
Gross Unrealized Losses	0	0
Fair Value	94	134
Public Utilities | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Cost or Amortized Cost	4,924
Public Utilities | Yen Denominated | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Cost or Amortized Cost		5,615
Gross Unrealized Gains	233	188
Gross Unrealized Losses	106	166
Fair Value	5,051	5,637
Sovereign and Supranational | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Cost or Amortized Cost	3,209
Sovereign and Supranational | Yen Denominated | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Cost or Amortized Cost		4,200
Gross Unrealized Gains	192	148
Gross Unrealized Losses	84	183
Fair Value	3,317	4,165
Banks/financial Institutions | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Cost or Amortized Cost	9,211
Banks/financial Institutions | Yen Denominated | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Cost or Amortized Cost		12,389
Gross Unrealized Gains	211	170
Gross Unrealized Losses	431	1,079
Fair Value	8,991	11,480
Other Corporate | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Cost or Amortized Cost	4,457
Other Corporate | Yen Denominated | Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Cost or Amortized Cost		5,348
Gross Unrealized Gains	187	149
Gross Unrealized Losses	108	185
Fair Value	$ 4,536	$ 5,312