INVESTMENTS - Fair Value and Gross Unrealized Losses for Securities That Have Been in Continuous Unrealized Loss Position (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	$ 21,653	$ 14,279
Total Unrealized Losses	1,826	834
Less than 12 months Fair Value	15,867	2,751
Less than 12 months Unrealized Losses	938	83
12 months or longer Fair Value	5,786	11,528
12 months or longer Unrealized Losses	888	751
Fixed Maturities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	20,908	13,496
Total Unrealized Losses	1,685	742
Less than 12 months Fair Value	15,652	2,557
Less than 12 months Unrealized Losses	911	78
12 months or longer Fair Value	5,256	10,939
12 months or longer Unrealized Losses	774	664
Perpetual securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	745	783
Total Unrealized Losses	141	92
Less than 12 months Fair Value	215	194
Less than 12 months Unrealized Losses	27	5
12 months or longer Fair Value	530	589
12 months or longer Unrealized Losses	114	87
Yen-denominated | Fixed Maturities | Japan government and agencies
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	92
Total Unrealized Losses	1
Less than 12 months Fair Value	92
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 | Public utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,451	805
Total Unrealized Losses	148	25
Less than 12 months Fair Value	1,039	98
Less than 12 months Unrealized Losses	102	1
12 months or longer Fair Value	412	707
12 months or longer Unrealized Losses	46	24
Yen-denominated | Fixed Maturities | Sovereign and supranational
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	728	359
Total Unrealized Losses	47	14
Less than 12 months Fair Value	535	0
Less than 12 months Unrealized Losses	32	0
12 months or longer Fair Value	193	359
12 months or longer Unrealized Losses	15	14
Yen-denominated | Fixed Maturities | Banks/financial institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	2,809	1,828
Total Unrealized Losses	254	267
Less than 12 months Fair Value	1,762	166
Less than 12 months Unrealized Losses	72	0
12 months or longer Fair Value	1,047	1,662
12 months or longer Unrealized Losses	182	267
Yen-denominated | Fixed Maturities | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,237	1,151
Total Unrealized Losses	88	60
Less than 12 months Fair Value	437	122
Less than 12 months Unrealized Losses	5	2
12 months or longer Fair Value	800	1,029
12 months or longer Unrealized Losses	83	58
Yen-denominated | Perpetual securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	739	783
Total Unrealized Losses	140	92
Less than 12 months Fair Value	215	194
Less than 12 months Unrealized Losses	27	5
12 months or longer Fair Value	524	589
12 months or longer Unrealized Losses	113	87
Dollar-denominated | Fixed Maturities | Municipalities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	44	75
Total Unrealized Losses	9	2
Less than 12 months Fair Value	44	53
Less than 12 months Unrealized Losses	9	1
12 months or longer Fair Value	0	22
12 months or longer Unrealized Losses	0	1
Dollar-denominated | Fixed Maturities | Public utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,955	1,001
Total Unrealized Losses	129	36
Less than 12 months Fair Value	1,499	164
Less than 12 months Unrealized Losses	79	7
12 months or longer Fair Value	456	837
12 months or longer Unrealized Losses	50	29
Dollar-denominated | Fixed Maturities | Banks/financial institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	307	205
Total Unrealized Losses	14	8
Less than 12 months Fair Value	304	53
Less than 12 months Unrealized Losses	14	5
12 months or longer Fair Value	3	152
12 months or longer Unrealized Losses	0	3
Dollar-denominated | Fixed Maturities | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	12,285	8,072
Total Unrealized Losses	995	330
Less than 12 months Fair Value	9,940	1,901
Less than 12 months Unrealized Losses	597	62
12 months or longer Fair Value	2,345	6,171
12 months or longer Unrealized Losses	398	$ 268
Dollar-denominated | Perpetual securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	6
Total Unrealized Losses	1
Less than 12 months Fair Value	0
Less than 12 months Unrealized Losses	0
12 months or longer Fair Value	6
12 months or longer Unrealized Losses	$ 1