INVESTMENTS - Fair Value and Gross Unrealized Losses for Securities That Have Been in Continuous Unrealized Loss Position (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	$ 18,724	$ 22,413
Total Unrealized Losses	1,729	2,013
Less than 12 months Fair Value	8,450	16,529
Less than 12 months Unrealized Losses	522	1,040
12 months or longer Fair Value	10,274	5,884
12 months or longer Unrealized Losses	1,207	973
Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	17,554	21,571
Total Unrealized Losses	1,509	1,915
Less than 12 months Fair Value	7,703	16,122
Less than 12 months Unrealized Losses	425	1,024
12 months or longer Fair Value	9,851	5,449
12 months or longer Unrealized Losses	1,084	891
Perpetual securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	815	651
Total Unrealized Losses	172	94
Less than 12 months Fair Value	392	216
Less than 12 months Unrealized Losses	49	12
12 months or longer Fair Value	423	435
12 months or longer Unrealized Losses	123	82
Equity securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	355	191
Total Unrealized Losses	48	4
Less than 12 months Fair Value	355	191
Less than 12 months Unrealized Losses	48	4
12 months or longer Fair Value	0	0
12 months or longer Unrealized Losses	0	0
Dollar-denominated | Fixed maturities | Municipalities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	44	80
Total Unrealized Losses	9	6
Less than 12 months Fair Value	0	80
Less than 12 months Unrealized Losses	0	6
12 months or longer Fair Value	44	0
12 months or longer Unrealized Losses	9	0
Dollar-denominated | Fixed maturities | Public utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,491	2,127
Total Unrealized Losses	132	221
Less than 12 months Fair Value	662	1,689
Less than 12 months Unrealized Losses	38	132
12 months or longer Fair Value	829	438
12 months or longer Unrealized Losses	94	89
Dollar-denominated | Fixed maturities | Banks/financial institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	211	366
Total Unrealized Losses	15	21
Less than 12 months Fair Value	184	348
Less than 12 months Unrealized Losses	6	11
12 months or longer Fair Value	27	18
12 months or longer Unrealized Losses	9	10
Dollar-denominated | Fixed maturities | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	10,079	13,430
Total Unrealized Losses	935	1,302
Less than 12 months Fair Value	4,167	11,068
Less than 12 months Unrealized Losses	282	770
12 months or longer Fair Value	5,912	2,362
12 months or longer Unrealized Losses	653	532
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	1,526	1,487
Total Unrealized Losses	89	104
Less than 12 months Fair Value	725	1,062
Less than 12 months Unrealized Losses	47	73
12 months or longer Fair Value	801	425
12 months or longer Unrealized Losses	42	31
Yen-denominated | Fixed maturities | Sovereign and supranational
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	309	580
Total Unrealized Losses	11	26
Less than 12 months Fair Value	97	385
Less than 12 months Unrealized Losses	1	13
12 months or longer Fair Value	212	195
12 months or longer Unrealized Losses	10	13
Yen-denominated | Fixed maturities | Banks/financial institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	2,108	2,350
Total Unrealized Losses	206	158
Less than 12 months Fair Value	949	1,147
Less than 12 months Unrealized Losses	12	14
12 months or longer Fair Value	1,159	1,203
12 months or longer Unrealized Losses	194	144
Yen-denominated | Fixed maturities | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,786	1,151
Total Unrealized Losses	112	77
Less than 12 months Fair Value	919	343
Less than 12 months Unrealized Losses	39	5
12 months or longer Fair Value	867	808
12 months or longer Unrealized Losses	73	72
Yen-denominated | Perpetual securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	815	645
Total Unrealized Losses	172	93
Less than 12 months Fair Value	392	216
Less than 12 months Unrealized Losses	49	12
12 months or longer Fair Value	423	429
12 months or longer Unrealized Losses	123	81
Yen-denominated | Equity securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	355	191
Total Unrealized Losses	48	4
Less than 12 months Fair Value	355	191
Less than 12 months Unrealized Losses	48	4
12 months or longer Fair Value	0	0
12 months or longer Unrealized Losses	$ 0	$ 0