INVESTMENTS - Fair Value and Gross Unrealized Losses for Securities That Have Been in Continuous Unrealized Loss Position (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	$ 10,858	$ 14,279
Total Unrealized Losses	719	834
Less than 12 months Fair Value	4,788	2,751
Less than 12 months Unrealized Losses	138	83
12 months or longer Fair Value	6,070	11,528
12 months or longer Unrealized Losses	581	751
Fixed Maturities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	10,133	13,496
Total Unrealized Losses	634	742
Less than 12 months Fair Value	4,666	2,557
Less than 12 months Unrealized Losses	135	78
12 months or longer Fair Value	5,467	10,939
12 months or longer Unrealized Losses	499	664
Perpetual securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	725	783
Total Unrealized Losses	85	92
Less than 12 months Fair Value	122	194
Less than 12 months Unrealized Losses	3	5
12 months or longer Fair Value	603	589
12 months or longer Unrealized Losses	82	87
Dollar-denominated | Fixed Maturities | Municipalities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	73	75
Total Unrealized Losses	3	2
Less than 12 months Fair Value	51	53
Less than 12 months Unrealized Losses	3	1
12 months or longer Fair Value	22	22
12 months or longer Unrealized Losses	0	1
Dollar-denominated | Fixed Maturities | Public Utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	795	1,001
Total Unrealized Losses	23	36
Less than 12 months Fair Value	404	164
Less than 12 months Unrealized Losses	9	7
12 months or longer Fair Value	391	837
12 months or longer Unrealized Losses	14	29
Dollar-denominated | Fixed Maturities | Banks/financial Institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	115	205
Total Unrealized Losses	5	8
Less than 12 months Fair Value	115	53
Less than 12 months Unrealized Losses	5	5
12 months or longer Fair Value	0	152
12 months or longer Unrealized Losses	0	3
Dollar-denominated | Fixed Maturities | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	4,701	8,072
Total Unrealized Losses	238	330
Less than 12 months Fair Value	2,278	1,901
Less than 12 months Unrealized Losses	88	62
12 months or longer Fair Value	2,423	6,171
12 months or longer Unrealized Losses	150	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
Yen-denominated | Fixed Maturities | Public Utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	761	805
Total Unrealized Losses	29	25
Less than 12 months Fair Value	421	98
Less than 12 months Unrealized Losses	11	1
12 months or longer Fair Value	340	707
12 months or longer Unrealized Losses	18	24
Yen-denominated | Fixed Maturities | Sovereign and supranational
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	366	359
Total Unrealized Losses	8	14
Less than 12 months Fair Value	166	0
Less than 12 months Unrealized Losses	0	0
12 months or longer Fair Value	200	359
12 months or longer Unrealized Losses	8	14
Yen-denominated | Fixed Maturities | Banks/financial Institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	2,324	1,828
Total Unrealized Losses	276	267
Less than 12 months Fair Value	1,107	166
Less than 12 months Unrealized Losses	16	0
12 months or longer Fair Value	1,217	1,662
12 months or longer Unrealized Losses	260	267
Yen-denominated | Fixed Maturities | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	998	1,151
Total Unrealized Losses	52	60
Less than 12 months Fair Value	124	122
Less than 12 months Unrealized Losses	3	2
12 months or longer Fair Value	874	1,029
12 months or longer Unrealized Losses	49	58
Yen-denominated | Perpetual securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	719	783
Total Unrealized Losses	84	92
Less than 12 months Fair Value	122	194
Less than 12 months Unrealized Losses	3	5
12 months or longer Fair Value	597	589
12 months or longer Unrealized Losses	$ 81	$ 87