INVESTMENTS - Fair Value and Gross Unrealized Losses for Securities That Have Been in Continuous Unrealized Loss Position (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	$ 38,223	$ 40,707
Total Unrealized Losses	4,025	1,582
Less than 12 months Fair Value	32,124	28,268
Less than 12 months Unrealized Losses	2,534	368
12 months or longer Fair Value	6,099	12,439
12 months or longer Unrealized Losses	1,491	1,214
Fixed Maturities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	36,319	39,250
Total Unrealized Losses	3,480	1,411
Less than 12 months Fair Value	30,766	28,145
Less than 12 months Unrealized Losses	2,234	368
12 months or longer Fair Value	5,553	11,105
12 months or longer Unrealized Losses	1,246	1,043
Fixed Maturities | Japan government and agencies | Yen Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	4,723	17,342
Total Unrealized Losses	84	148
Less than 12 months Fair Value	4,723	17,342
Less than 12 months Unrealized Losses	84	148
12 months or longer Fair Value	0	0
12 months or longer Unrealized Losses	0	0
Fixed Maturities | Municipalities | Dollar Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	121	34
Total Unrealized Losses	8	6
Less than 12 months Fair Value	86	1
Less than 12 months Unrealized Losses	4	0
12 months or longer Fair Value	35	33
12 months or longer Unrealized Losses	4	6
Fixed Maturities | Municipalities | Yen Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value		56
Total Unrealized Losses		2
Less than 12 months Fair Value		56
Less than 12 months Unrealized Losses		2
12 months or longer Fair Value		0
12 months or longer Unrealized Losses		0
Fixed Maturities | Mortgage- and asset-backed Securities | Dollar Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	7	10
Total Unrealized Losses	0	0
Less than 12 months Fair Value	7	10
Less than 12 months Unrealized Losses	0	0
12 months or longer Fair Value	0	0
12 months or longer Unrealized Losses	0	0
Fixed Maturities | Mortgage- and asset-backed Securities | Yen Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	120	136
Total Unrealized Losses	1	1
Less than 12 months Fair Value	0	0
Less than 12 months Unrealized Losses	0	0
12 months or longer Fair Value	120	136
12 months or longer Unrealized Losses	1	1
Fixed Maturities | Public Utilities | Dollar Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	2,182	736
Total Unrealized Losses	168	17
Less than 12 months Fair Value	2,182	736
Less than 12 months Unrealized Losses	168	17
12 months or longer Fair Value	0	0
12 months or longer Unrealized Losses	0	0
Fixed Maturities | Public Utilities | Yen Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	4,051	3,920
Total Unrealized Losses	370	178
Less than 12 months Fair Value	2,854	1,339
Less than 12 months Unrealized Losses	205	31
12 months or longer Fair Value	1,197	2,581
12 months or longer Unrealized Losses	165	147
Fixed Maturities | Sovereign and Supranational | Dollar Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	61	31
Total Unrealized Losses	4	2
Less than 12 months Fair Value	29	0
Less than 12 months Unrealized Losses	1	0
12 months or longer Fair Value	32	31
12 months or longer Unrealized Losses	3	2
Fixed Maturities | Sovereign and Supranational | Yen Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	913	1,244
Total Unrealized Losses	101	84
Less than 12 months Fair Value	545	507
Less than 12 months Unrealized Losses	13	13
12 months or longer Fair Value	368	737
12 months or longer Unrealized Losses	88	71
Fixed Maturities | Banks/financial Institutions | Dollar Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	786	276
Total Unrealized Losses	46	6
Less than 12 months Fair Value	759	180
Less than 12 months Unrealized Losses	43	3
12 months or longer Fair Value	27	96
12 months or longer Unrealized Losses	3	3
Fixed Maturities | Banks/financial Institutions | Yen Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	6,280	6,918
Total Unrealized Losses	1,061	611
Less than 12 months Fair Value	3,581	1,935
Less than 12 months Unrealized Losses	293	28
12 months or longer Fair Value	2,699	4,983
12 months or longer Unrealized Losses	768	583
Fixed Maturities | Other Corporate | Dollar Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	12,656	4,534
Total Unrealized Losses	1,107	95
Less than 12 months Fair Value	12,600	4,404
Less than 12 months Unrealized Losses	1,101	86
12 months or longer Fair Value	56	130
12 months or longer Unrealized Losses	6	9
Fixed Maturities | Other Corporate | Yen Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	4,381	4,013
Total Unrealized Losses	528	261
Less than 12 months Fair Value	3,362	1,635
Less than 12 months Unrealized Losses	320	40
12 months or longer Fair Value	1,019	2,378
12 months or longer Unrealized Losses	208	221
Fixed Maturities | US government and agencies | Dollar Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	38
Total Unrealized Losses	2
Less than 12 months Fair Value	38
Less than 12 months Unrealized Losses	2
12 months or longer Fair Value	0
12 months or longer Unrealized Losses	0
Perpetual Securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,903	1,451
Total Unrealized Losses	545	170
Less than 12 months Fair Value	1,357	120
Less than 12 months Unrealized Losses	300	0
12 months or longer Fair Value	546	1,331
12 months or longer Unrealized Losses	245	170
Perpetual Securities | Dollar Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	69	136
Total Unrealized Losses	15	9
Less than 12 months Fair Value	49	120
Less than 12 months Unrealized Losses	11	0
12 months or longer Fair Value	20	16
12 months or longer Unrealized Losses	4	9
Perpetual Securities | Yen Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,834	1,315
Total Unrealized Losses	530	161
Less than 12 months Fair Value	1,308	0
Less than 12 months Unrealized Losses	289	0
12 months or longer Fair Value	526	1,315
12 months or longer Unrealized Losses	241	161
Equity Securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1	6
Total Unrealized Losses	0	1
Less than 12 months Fair Value	1	3
Less than 12 months Unrealized Losses	0	0
12 months or longer Fair Value	0	3
12 months or longer Unrealized Losses	$ 0	$ 1