INVESTMENTS - Fair Value and Gross Unrealized Losses for Securities That Have Been in Continuous Unrealized Loss Position (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	$ 21,817	$ 14,279
Total Unrealized Losses	1,507	834
Less than 12 months Fair Value	16,218	2,751
Less than 12 months Unrealized Losses	767	83
12 months or longer Fair Value	5,599	11,528
12 months or longer Unrealized Losses	740	751
Fixed Maturities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	21,066	13,496
Total Unrealized Losses	1,397	742
Less than 12 months Fair Value	16,034	2,557
Less than 12 months Unrealized Losses	755	78
12 months or longer Fair Value	5,032	10,939
12 months or longer Unrealized Losses	642	664
Perpetual securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	751	783
Total Unrealized Losses	110	92
Less than 12 months Fair Value	184	194
Less than 12 months Unrealized Losses	12	5
12 months or longer Fair Value	567	589
12 months or longer Unrealized Losses	98	87
Yen-denominated | Fixed Maturities | Japan government and agencies
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	494
Total Unrealized Losses	6
Less than 12 months Fair Value	494
Less than 12 months Unrealized Losses	6
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	1,429	805
Total Unrealized Losses	75	25
Less than 12 months Fair Value	1,110	98
Less than 12 months Unrealized Losses	43	1
12 months or longer Fair Value	319	707
12 months or longer Unrealized Losses	32	24
Yen-denominated | Fixed Maturities | Sovereign and supranational
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	346	359
Total Unrealized Losses	21	14
Less than 12 months Fair Value	159	0
Less than 12 months Unrealized Losses	4	0
12 months or longer Fair Value	187	359
12 months or longer Unrealized Losses	17	14
Yen-denominated | Fixed Maturities | Banks/financial institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	3,063	1,828
Total Unrealized Losses	305	267
Less than 12 months Fair Value	1,872	166
Less than 12 months Unrealized Losses	47	0
12 months or longer Fair Value	1,191	1,662
12 months or longer Unrealized Losses	258	267
Yen-denominated | Fixed Maturities | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,075	1,151
Total Unrealized Losses	60	60
Less than 12 months Fair Value	387	122
Less than 12 months Unrealized Losses	5	2
12 months or longer Fair Value	688	1,029
12 months or longer Unrealized Losses	55	58
Yen-denominated | Perpetual securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	751	783
Total Unrealized Losses	110	92
Less than 12 months Fair Value	184	194
Less than 12 months Unrealized Losses	12	5
12 months or longer Fair Value	567	589
12 months or longer Unrealized Losses	98	87
Dollar-denominated | Fixed Maturities | Municipalities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	92	75
Total Unrealized Losses	10	2
Less than 12 months Fair Value	77	53
Less than 12 months Unrealized Losses	9	1
12 months or longer Fair Value	15	22
12 months or longer Unrealized Losses	1	1
Dollar-denominated | Fixed Maturities | Public utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	2,033	1,001
Total Unrealized Losses	118	36
Less than 12 months Fair Value	1,657	164
Less than 12 months Unrealized Losses	90	7
12 months or longer Fair Value	376	837
12 months or longer Unrealized Losses	28	29
Dollar-denominated | Fixed Maturities | Banks/financial institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	347	205
Total Unrealized Losses	20	8
Less than 12 months Fair Value	345	53
Less than 12 months Unrealized Losses	20	5
12 months or longer Fair Value	2	152
12 months or longer Unrealized Losses	0	3
Dollar-denominated | Fixed Maturities | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	12,187	8,072
Total Unrealized Losses	782	330
Less than 12 months Fair Value	9,933	1,901
Less than 12 months Unrealized Losses	531	62
12 months or longer Fair Value	2,254	6,171
12 months or longer Unrealized Losses	$ 251	$ 268