INVESTMENTS - Fair Value and Gross Unrealized Losses for Securities That Have Been in Continuous Unrealized Loss Position (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	$ 14,279	$ 36,214
Total Unrealized Losses	834	2,746
Less Than 12 months Fair Value	2,751	27,790
Less Than 12 months Unrealized Losses	83	1,376
12 months or longer Fair Value	11,528	8,424
12 months or longer Unrealized Losses	751	1,370
Fixed Maturities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	13,496	34,828
Total Unrealized Losses	742	2,519
Less Than 12 months Fair Value	2,557	26,985
Less Than 12 months Unrealized Losses	78	1,293
12 months or longer Fair Value	10,939	7,843
12 months or longer Unrealized Losses	664	1,226
Perpetual securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	783	1,381
Total Unrealized Losses	92	226
Less Than 12 months Fair Value	194	800
Less Than 12 months Unrealized Losses	5	82
12 months or longer Fair Value	589	581
12 months or longer Unrealized Losses	87	144
Equity securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value		5
Total Unrealized Losses		1
Less Than 12 months Fair Value		5
Less Than 12 months Unrealized Losses		1
12 months or longer Fair Value		0
12 months or longer Unrealized Losses		0
Yen-denominated | Fixed Maturities | Japan government and agencies
Investments, Unrealized Loss Position [Line Items]
Total Fair Value		8,869
Total Unrealized Losses		34
Less Than 12 months Fair Value		8,869
Less Than 12 months Unrealized Losses		34
12 months or longer Fair Value		0
12 months or longer Unrealized Losses		0
Yen-denominated | Fixed Maturities | Public utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	805	2,519
Total Unrealized Losses	25	140
Less Than 12 months Fair Value	98	1,816
Less Than 12 months Unrealized Losses	1	54
12 months or longer Fair Value	707	703
12 months or longer Unrealized Losses	24	86
Yen-denominated | Fixed Maturities | Sovereign and supranational
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	359	1,152
Total Unrealized Losses	14	100
Less Than 12 months Fair Value	0	791
Less Than 12 months Unrealized Losses	0	34
12 months or longer Fair Value	359	361
12 months or longer Unrealized Losses	14	66
Yen-denominated | Fixed Maturities | Banks/financial Institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,828	4,533
Total Unrealized Losses	267	570
Less Than 12 months Fair Value	166	2,322
Less Than 12 months Unrealized Losses	0	107
12 months or longer Fair Value	1,662	2,211
12 months or longer Unrealized Losses	267	463
Yen-denominated | Fixed Maturities | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,151	3,372
Total Unrealized Losses	60	272
Less Than 12 months Fair Value	122	2,296
Less Than 12 months Unrealized Losses	2	152
12 months or longer Fair Value	1,029	1,076
12 months or longer Unrealized Losses	58	120
Yen-denominated | Perpetual securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	783	1,322
Total Unrealized Losses	92	217
Less Than 12 months Fair Value	194	748
Less Than 12 months Unrealized Losses	5	74
12 months or longer Fair Value	589	574
12 months or longer Unrealized Losses	87	143
Dollar-denominated | Fixed Maturities | Municipalities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	75	177
Total Unrealized Losses	2	12
Less Than 12 months Fair Value	53	145
Less Than 12 months Unrealized Losses	1	8
12 months or longer Fair Value	22	32
12 months or longer Unrealized Losses	1	4
Dollar-denominated | Fixed Maturities | Public utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,001	2,023
Total Unrealized Losses	36	183
Less Than 12 months Fair Value	164	1,740
Less Than 12 months Unrealized Losses	7	143
12 months or longer Fair Value	837	283
12 months or longer Unrealized Losses	29	40
Dollar-denominated | Fixed Maturities | Sovereign and supranational
Investments, Unrealized Loss Position [Line Items]
Total Fair Value		12
Total Unrealized Losses		1
Less Than 12 months Fair Value		12
Less Than 12 months Unrealized Losses		1
12 months or longer Fair Value		0
12 months or longer Unrealized Losses		0
Dollar-denominated | Fixed Maturities | Banks/financial Institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	205	547
Total Unrealized Losses	8	33
Less Than 12 months Fair Value	53	454
Less Than 12 months Unrealized Losses	5	23
12 months or longer Fair Value	152	93
12 months or longer Unrealized Losses	3	10
Dollar-denominated | Fixed Maturities | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	8,072	11,588
Total Unrealized Losses	330	1,170
Less Than 12 months Fair Value	1,901	8,504
Less Than 12 months Unrealized Losses	62	733
12 months or longer Fair Value	6,171	3,084
12 months or longer Unrealized Losses	268	437
Dollar-denominated | Fixed Maturities | US government and agencies
Investments, Unrealized Loss Position [Line Items]
Total Fair Value		36
Total Unrealized Losses		4
Less Than 12 months Fair Value		36
Less Than 12 months Unrealized Losses		4
12 months or longer Fair Value		0
12 months or longer Unrealized Losses		0
Dollar-denominated | Perpetual securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value		59
Total Unrealized Losses		9
Less Than 12 months Fair Value		52
Less Than 12 months Unrealized Losses		8
12 months or longer Fair Value		7
12 months or longer Unrealized Losses		$ 1