INVESTMENTS - Fair Value and Gross Unrealized Losses for Securities That Have Been in Continuous Unrealized Loss Position (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	$ 33,848	$ 40,697
Total Unrealized Losses	3,656	1,582
Less than 12 months Fair Value	27,230	28,258
Less than 12 months Unrealized Losses	2,320	368
12 months or longer Fair Value	6,618	12,439
12 months or longer Unrealized Losses	1,336	1,214
Fixed Maturities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	31,856	39,240
Total Unrealized Losses	3,173	1,411
Less than 12 months Fair Value	25,812	28,135
Less than 12 months Unrealized Losses	2,062	368
12 months or longer Fair Value	6,044	11,105
12 months or longer Unrealized Losses	1,111	1,043
Fixed Maturities | Japan government and agencies | Yen Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,933	17,342
Total Unrealized Losses	22	148
Less than 12 months Fair Value	1,933	17,342
Less than 12 months Unrealized Losses	22	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	196	34
Total Unrealized Losses	15	6
Less than 12 months Fair Value	163	1
Less than 12 months Unrealized Losses	10	0
12 months or longer Fair Value	33	33
12 months or longer Unrealized Losses	5	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 | Yen Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value		136
Total Unrealized Losses		1
Less than 12 months Fair Value		0
Less than 12 months Unrealized Losses		0
12 months or longer Fair Value		136
12 months or longer Unrealized Losses		1
Fixed Maturities | Public Utilities | Dollar Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	2,314	736
Total Unrealized Losses	206	17
Less than 12 months Fair Value	2,297	736
Less than 12 months Unrealized Losses	203	17
12 months or longer Fair Value	17	0
12 months or longer Unrealized Losses	3	0
Fixed Maturities | Public Utilities | Yen Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	3,367	3,920
Total Unrealized Losses	262	178
Less than 12 months Fair Value	2,123	1,339
Less than 12 months Unrealized Losses	134	31
12 months or longer Fair Value	1,244	2,581
12 months or longer Unrealized Losses	128	147
Fixed Maturities | Sovereign and Supranational | Dollar Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	43	31
Total Unrealized Losses	1	2
Less than 12 months Fair Value	43	0
Less than 12 months Unrealized Losses	1	0
12 months or longer Fair Value	0	31
12 months or longer Unrealized Losses	0	2
Fixed Maturities | Sovereign and Supranational | Yen Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	935	1,244
Total Unrealized Losses	104	84
Less than 12 months Fair Value	554	507
Less than 12 months Unrealized Losses	25	13
12 months or longer Fair Value	381	737
12 months or longer Unrealized Losses	79	71
Fixed Maturities | Banks/financial Institutions | Dollar Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	816	276
Total Unrealized Losses	48	6
Less than 12 months Fair Value	784	180
Less than 12 months Unrealized Losses	44	3
12 months or longer Fair Value	32	96
12 months or longer Unrealized Losses	4	3
Fixed Maturities | Banks/financial Institutions | Yen Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	5,455	6,918
Total Unrealized Losses	815	611
Less than 12 months Fair Value	2,704	1,935
Less than 12 months Unrealized Losses	171	28
12 months or longer Fair Value	2,751	4,983
12 months or longer Unrealized Losses	644	583
Fixed Maturities | Other Corporate | Dollar Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	12,903	4,534
Total Unrealized Losses	1,278	95
Less than 12 months Fair Value	12,532	4,404
Less than 12 months Unrealized Losses	1,207	86
12 months or longer Fair Value	371	130
12 months or longer Unrealized Losses	71	9
Fixed Maturities | Other Corporate | Yen Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	3,857	4,013
Total Unrealized Losses	419	261
Less than 12 months Fair Value	2,642	1,635
Less than 12 months Unrealized Losses	242	40
12 months or longer Fair Value	1,215	2,378
12 months or longer Unrealized Losses	177	221
Fixed Maturities | US government and agencies | Dollar Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	37
Total Unrealized Losses	3
Less than 12 months Fair Value	37
Less than 12 months Unrealized Losses	3
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	1,987	1,451
Total Unrealized Losses	482	170
Less than 12 months Fair Value	1,413	120
Less than 12 months Unrealized Losses	257	0
12 months or longer Fair Value	574	1,331
12 months or longer Unrealized Losses	225	170
Perpetual Securities | Dollar Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	71	136
Total Unrealized Losses	14	9
Less than 12 months Fair Value	51	120
Less than 12 months Unrealized Losses	9	0
12 months or longer Fair Value	20	16
12 months or longer Unrealized Losses	5	9
Perpetual Securities | Yen Denominated
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,916	1,315
Total Unrealized Losses	468	161
Less than 12 months Fair Value	1,362	0
Less than 12 months Unrealized Losses	248	0
12 months or longer Fair Value	554	1,315
12 months or longer Unrealized Losses	220	161
Equity Securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	5	6
Total Unrealized Losses	1	1
Less than 12 months Fair Value	5	3
Less than 12 months Unrealized Losses	1	0
12 months or longer Fair Value	0	3
12 months or longer Unrealized Losses	$ 0	$ 1