INVESTMENTS - Fair Value and Gross Unrealized Losses for Securities That Have Been in Continuous Unrealized Loss Position (Detail) - Fixed maturities - USD ($) $ in Millions		6 Months Ended	12 Months Ended
		Jun. 30, 2018	Dec. 31, 2017
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	$ 22,933	$ 16,685
Total Unrealized Losses	[1]	1,451	813
Less than 12 months Fair Value	[1]	12,822	5,776
Less than 12 months Unrealized Losses	[1]	522	77
12 months or longer Fair Value	[1]	10,111	10,909
12 months or longer Unrealized Losses	[1]	929	736
Dollar-denominated | U.S. government and agencies
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	78	74
Total Unrealized Losses	[1]	1	1
Less than 12 months Fair Value	[1]	74	74
Less than 12 months Unrealized Losses	[1]	1	1
12 months or longer Fair Value	[1]	4	0
12 months or longer Unrealized Losses	[1]	0	0
Dollar-denominated | Municipalities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	261
Total Unrealized Losses	[1]	1
Less than 12 months Fair Value	[1]	261
Less than 12 months Unrealized Losses	[1]	1
12 months or longer Fair Value	[1]	0
12 months or longer Unrealized Losses	[1]	0
Dollar-denominated | Mortgage- and asset-backed securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	86
Total Unrealized Losses	[1]	1
Less than 12 months Fair Value	[1]	71
Less than 12 months Unrealized Losses	[1]	1
12 months or longer Fair Value	[1]	15
12 months or longer Unrealized Losses	[1]	0
Dollar-denominated | Public utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	1,664	785
Total Unrealized Losses	[1]	103	27
Less than 12 months Fair Value	[1]	1,200	221
Less than 12 months Unrealized Losses	[1]	52	3
12 months or longer Fair Value	[1]	464	564
12 months or longer Unrealized Losses	[1]	51	24
Dollar-denominated | Sovereign and supranational
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	13
Total Unrealized Losses	[1]	0
Less than 12 months Fair Value	[1]	13
Less than 12 months Unrealized Losses	[1]	0
12 months or longer Fair Value	[1]	0
12 months or longer Unrealized Losses	[1]	0
Dollar-denominated | Banks/financial institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	696	362
Total Unrealized Losses	[1]	30	8
Less than 12 months Fair Value	[1]	561	316
Less than 12 months Unrealized Losses	[1]	20	5
12 months or longer Fair Value	[1]	135	46
12 months or longer Unrealized Losses	[1]	10	3
Dollar-denominated | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	13,044	7,741
Total Unrealized Losses	[1]	980	418
Less than 12 months Fair Value	[1]	8,391	2,839
Less than 12 months Unrealized Losses	[1]	362	50
12 months or longer Fair Value	[1]	4,653	4,902
12 months or longer Unrealized Losses	[1]	618	368
Yen-denominated | Japan government and agencies
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	3,647	5,255
Total Unrealized Losses	[1]	150	271
Less than 12 months Fair Value	[1]	0	1,264
Less than 12 months Unrealized Losses	[1]	0	9
12 months or longer Fair Value	[1]	3,647	3,991
12 months or longer Unrealized Losses	[1]	150	262
Yen-denominated | Municipalities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	137	129
Total Unrealized Losses	[1]	9	12
Less than 12 months Fair Value	[1]	13	10
Less than 12 months Unrealized Losses	[1]	0	0
12 months or longer Fair Value	[1]	124	119
12 months or longer Unrealized Losses	[1]	9	12
Yen-denominated | Public utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	268	83
Total Unrealized Losses	[1]	4	6
Less than 12 months Fair Value	[1]	180	0
Less than 12 months Unrealized Losses	[1]	1	0
12 months or longer Fair Value	[1]	88	83
12 months or longer Unrealized Losses	[1]	3	6
Yen-denominated | Sovereign and supranational
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	286	309
Total Unrealized Losses	[1]	30	1
Less than 12 months Fair Value	[1]	286	309
Less than 12 months Unrealized Losses	[1]	30	1
12 months or longer Fair Value	[1]	0	0
12 months or longer Unrealized Losses	[1]	0	0
Yen-denominated | Banks/financial institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	2,344	1,507
Total Unrealized Losses	[1]	136	62
Less than 12 months Fair Value	[1]	1,478	394
Less than 12 months Unrealized Losses	[1]	50	4
12 months or longer Fair Value	[1]	866	1,113
12 months or longer Unrealized Losses	[1]	86	58
Yen-denominated | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	409	440
Total Unrealized Losses	[1]	6	7
Less than 12 months Fair Value	[1]	294	349
Less than 12 months Unrealized Losses	[1]	4	4
12 months or longer Fair Value	[1]	115	91
12 months or longer Unrealized Losses	[1]	$ 2	$ 3

[1] Includes perpetual securities