INVESTMENTS - Fair Value and Gross Unrealized Losses for Securities That Have Been in Continuous Unrealized Loss Position (Detail) - Fixed maturity securities - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	$ 28,481	$ 31,709
Total Unrealized Losses	3,082	4,528
Less than 12 months Fair Value	7,880	20,347
Less than 12 months Unrealized Losses	462	2,213
12 months or Longer Fair Value	20,601	11,362
12 months or Longer Unrealized Losses	2,620	2,315
Dollar-denominated | U.S. government and agencies
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	149	159
Total Unrealized Losses	5	8
Less than 12 months Fair Value	62	85
Less than 12 months Unrealized Losses	1	3
12 months or Longer Fair Value	87	74
12 months or Longer Unrealized Losses	4	5
Dollar-denominated | Municipalities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	817	854
Total Unrealized Losses	55	89
Less than 12 months Fair Value	356	735
Less than 12 months Unrealized Losses	13	57
12 months or Longer Fair Value	461	119
12 months or Longer Unrealized Losses	42	32
Dollar-denominated | Mortgage- and asset-backed securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,007	936
Total Unrealized Losses	69	84
Less than 12 months Fair Value	753	640
Less than 12 months Unrealized Losses	58	42
12 months or Longer Fair Value	254	296
12 months or Longer Unrealized Losses	11	42
Dollar-denominated | Public utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,380	1,852
Total Unrealized Losses	128	180
Less than 12 months Fair Value	776	1,667
Less than 12 months Unrealized Losses	53	144
12 months or Longer Fair Value	604	185
12 months or Longer Unrealized Losses	75	36
Dollar-denominated | Sovereign and supranational
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	31	30
Total Unrealized Losses	11	12
Less than 12 months Fair Value	0	0
Less than 12 months Unrealized Losses	0	0
12 months or Longer Fair Value	31	30
12 months or Longer Unrealized Losses	11	12
Dollar-denominated | Banks/financial institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	982	1,147
Total Unrealized Losses	85	105
Less than 12 months Fair Value	448	786
Less than 12 months Unrealized Losses	17	58
12 months or Longer Fair Value	534	361
12 months or Longer Unrealized Losses	68	47
Dollar-denominated | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	8,128	10,529
Total Unrealized Losses	798	1,201
Less than 12 months Fair Value	3,297	8,636
Less than 12 months Unrealized Losses	119	785
12 months or Longer Fair Value	4,831	1,893
12 months or Longer Unrealized Losses	679	416
Yen-denominated | Japan government and agencies
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	8,845	8,856
Total Unrealized Losses	1,079	1,724
Less than 12 months Fair Value	565	3,733
Less than 12 months Unrealized Losses	77	580
12 months or Longer Fair Value	8,280	5,123
12 months or Longer Unrealized Losses	1,002	1,144
Yen-denominated | Municipalities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	303	286
Total Unrealized Losses	42	61
Less than 12 months Fair Value	57	150
Less than 12 months Unrealized Losses	4	26
12 months or Longer Fair Value	246	136
12 months or Longer Unrealized Losses	38	35
Yen-denominated | Mortgage- and asset-backed securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	70	62
Total Unrealized Losses	8	12
Less than 12 months Fair Value	5	38
Less than 12 months Unrealized Losses	0	6
12 months or Longer Fair Value	65	24
12 months or Longer Unrealized Losses	8	6
Yen-denominated | Public utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	726	880
Total Unrealized Losses	63	108
Less than 12 months Fair Value	37	576
Less than 12 months Unrealized Losses	2	61
12 months or Longer Fair Value	689	304
12 months or Longer Unrealized Losses	61	47
Yen-denominated | Sovereign and supranational
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	72	71
Total Unrealized Losses	3	5
Less than 12 months Fair Value	35	34
Less than 12 months Unrealized Losses	3	4
12 months or Longer Fair Value	37	37
12 months or Longer Unrealized Losses	0	1
Yen-denominated | Banks/financial institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	3,907	3,957
Total Unrealized Losses	427	531
Less than 12 months Fair Value	736	1,760
Less than 12 months Unrealized Losses	43	174
12 months or Longer Fair Value	3,171	2,197
12 months or Longer Unrealized Losses	384	357
Yen-denominated | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	2,064	2,090
Total Unrealized Losses	309	408
Less than 12 months Fair Value	753	1,507
Less than 12 months Unrealized Losses	72	273
12 months or Longer Fair Value	1,311	583
12 months or Longer Unrealized Losses	$ 237	$ 135