INVESTMENTS - Fair Value and Gross Unrealized Losses for Securities That Have Been in Continuous Unrealized Loss Position (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	$ 20,275	$ 22,413
Total Unrealized Losses	1,156	2,013
Less Than 12 months Fair Value	14,743	16,529
Less Than 12 months Unrealized Losses	621	1,040
12 months or longer Fair Value	5,532	5,884
12 months or longer Unrealized Losses	535	973
Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	19,536	21,571
Total Unrealized Losses	1,099	1,915
Less Than 12 months Fair Value	14,398	16,122
Less Than 12 months Unrealized Losses	612	1,024
12 months or longer Fair Value	5,138	5,449
12 months or longer Unrealized Losses	487	891
Perpetual securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	479	651
Total Unrealized Losses	49	94
Less Than 12 months Fair Value	85	216
Less Than 12 months Unrealized Losses	1	12
12 months or longer Fair Value	394	435
12 months or longer Unrealized Losses	48	82
Equity securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	260	191
Total Unrealized Losses	8	4
Less Than 12 months Fair Value	260	191
Less Than 12 months Unrealized Losses	8	4
12 months or longer Fair Value	0	0
12 months or longer Unrealized Losses	0	0
Yen-denominated | Fixed maturities | Japan government and agencies
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	3,958
Total Unrealized Losses	160
Less Than 12 months Fair Value	3,958
Less Than 12 months Unrealized Losses	160
12 months or longer Fair Value	0
12 months or longer Unrealized Losses	0
Yen-denominated | Fixed maturities | Municipalities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	105
Total Unrealized Losses	8
Less Than 12 months Fair Value	105
Less Than 12 months Unrealized Losses	8
12 months or longer Fair Value	0
12 months or longer Unrealized Losses	0
Yen-denominated | Fixed maturities | Mortgage- and asset-backed securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	713
Total Unrealized Losses	8
Less Than 12 months Fair Value	713
Less Than 12 months Unrealized Losses	8
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	635	1,487
Total Unrealized Losses	26	104
Less Than 12 months Fair Value	347	1,062
Less Than 12 months Unrealized Losses	14	73
12 months or longer Fair Value	288	425
12 months or longer Unrealized Losses	12	31
Yen-denominated | Fixed maturities | Sovereign and supranational
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	244	580
Total Unrealized Losses	13	26
Less Than 12 months Fair Value	38	385
Less Than 12 months Unrealized Losses	5	13
12 months or longer Fair Value	206	195
12 months or longer Unrealized Losses	8	13
Yen-denominated | Fixed maturities | Banks/financial institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,521	2,350
Total Unrealized Losses	100	158
Less Than 12 months Fair Value	636	1,147
Less Than 12 months Unrealized Losses	19	14
12 months or longer Fair Value	885	1,203
12 months or longer Unrealized Losses	81	144
Yen-denominated | Fixed maturities | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	321	1,151
Total Unrealized Losses	10	77
Less Than 12 months Fair Value	321	343
Less Than 12 months Unrealized Losses	10	5
12 months or longer Fair Value	0	808
12 months or longer Unrealized Losses	0	72
Yen-denominated | Perpetual securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	479	645
Total Unrealized Losses	49	93
Less Than 12 months Fair Value	85	216
Less Than 12 months Unrealized Losses	1	12
12 months or longer Fair Value	394	429
12 months or longer Unrealized Losses	48	81
Yen-denominated | Equity securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	49	191
Total Unrealized Losses	2	4
Less Than 12 months Fair Value	49	191
Less Than 12 months Unrealized Losses	2	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	8	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	8	0
Dollar-denominated | Fixed maturities | Public utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,265	2,127
Total Unrealized Losses	60	221
Less Than 12 months Fair Value	790	1,689
Less Than 12 months Unrealized Losses	32	132
12 months or longer Fair Value	475	438
12 months or longer Unrealized Losses	28	89
Dollar-denominated | Fixed maturities | Banks/financial institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	268	366
Total Unrealized Losses	16	21
Less Than 12 months Fair Value	238	348
Less Than 12 months Unrealized Losses	10	11
12 months or longer Fair Value	30	18
12 months or longer Unrealized Losses	6	10
Dollar-denominated | Fixed maturities | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	10,462	13,430
Total Unrealized Losses	690	1,302
Less Than 12 months Fair Value	7,252	11,068
Less Than 12 months Unrealized Losses	346	770
12 months or longer Fair Value	3,210	2,362
12 months or longer Unrealized Losses	344	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
Dollar-denominated | Equity securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	211
Total Unrealized Losses	6
Less Than 12 months Fair Value	211
Less Than 12 months Unrealized Losses	6
12 months or longer Fair Value	0
12 months or longer Unrealized Losses	$ 0