INVESTMENTS - Fair Value and Gross Unrealized Losses for Securities That Have Been in Continuous Unrealized Loss Position (Detail) - Fixed maturity securities - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	$ 28,535	$ 31,709
Total Unrealized Losses	4,421	4,528
Less than 12 months Fair Value	7,104	20,347
Less than 12 months Unrealized Losses	419	2,213
12 months or Longer Fair Value	21,431	11,362
12 months or Longer Unrealized Losses	4,002	2,315
Dollar-denominated | U.S. government and agencies
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	179	159
Total Unrealized Losses	10	8
Less than 12 months Fair Value	42	85
Less than 12 months Unrealized Losses	1	3
12 months or Longer Fair Value	137	74
12 months or Longer Unrealized Losses	9	5
Dollar-denominated | Municipalities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	738	854
Total Unrealized Losses	112	89
Less than 12 months Fair Value	123	735
Less than 12 months Unrealized Losses	7	57
12 months or Longer Fair Value	615	119
12 months or Longer Unrealized Losses	105	32
Dollar-denominated | Mortgage- and asset-backed securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,094	936
Total Unrealized Losses	74	84
Less than 12 months Fair Value	804	640
Less than 12 months Unrealized Losses	61	42
12 months or Longer Fair Value	290	296
12 months or Longer Unrealized Losses	13	42
Dollar-denominated | Public utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,754	1,852
Total Unrealized Losses	238	180
Less than 12 months Fair Value	944	1,667
Less than 12 months Unrealized Losses	96	144
12 months or Longer Fair Value	810	185
12 months or Longer Unrealized Losses	142	36
Dollar-denominated | Sovereign and supranational
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	33	30
Total Unrealized Losses	9	12
Less than 12 months Fair Value	0	0
Less than 12 months Unrealized Losses	0	0
12 months or Longer Fair Value	33	30
12 months or Longer Unrealized Losses	9	12
Dollar-denominated | Banks/financial institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,043	1,147
Total Unrealized Losses	99	105
Less than 12 months Fair Value	460	786
Less than 12 months Unrealized Losses	16	58
12 months or Longer Fair Value	583	361
12 months or Longer Unrealized Losses	83	47
Dollar-denominated | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	8,831	10,529
Total Unrealized Losses	1,243	1,201
Less than 12 months Fair Value	2,994	8,636
Less than 12 months Unrealized Losses	166	785
12 months or Longer Fair Value	5,837	1,893
12 months or Longer Unrealized Losses	1,077	416
Yen-denominated | Japan government and agencies
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	7,997	8,856
Total Unrealized Losses	1,695	1,724
Less than 12 months Fair Value	656	3,733
Less than 12 months Unrealized Losses	24	580
12 months or Longer Fair Value	7,341	5,123
12 months or Longer Unrealized Losses	1,671	1,144
Yen-denominated | Municipalities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	283	286
Total Unrealized Losses	58	61
Less than 12 months Fair Value	32	150
Less than 12 months Unrealized Losses	0	26
12 months or Longer Fair Value	251	136
12 months or Longer Unrealized Losses	58	35
Yen-denominated | Mortgage- and asset-backed securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	54	62
Total Unrealized Losses	11	12
Less than 12 months Fair Value	0	38
Less than 12 months Unrealized Losses	0	6
12 months or Longer Fair Value	54	24
12 months or Longer Unrealized Losses	11	6
Yen-denominated | Public utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	963	880
Total Unrealized Losses	89	108
Less than 12 months Fair Value	415	576
Less than 12 months Unrealized Losses	18	61
12 months or Longer Fair Value	548	304
12 months or Longer Unrealized Losses	71	47
Yen-denominated | Sovereign and supranational
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	58	71
Total Unrealized Losses	6	5
Less than 12 months Fair Value	0	34
Less than 12 months Unrealized Losses	0	4
12 months or Longer Fair Value	58	37
12 months or Longer Unrealized Losses	6	1
Yen-denominated | Banks/financial institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	3,491	3,957
Total Unrealized Losses	403	531
Less than 12 months Fair Value	110	1,760
Less than 12 months Unrealized Losses	3	174
12 months or Longer Fair Value	3,381	2,197
12 months or Longer Unrealized Losses	400	357
Yen-denominated | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	2,017	2,090
Total Unrealized Losses	374	408
Less than 12 months Fair Value	524	1,507
Less than 12 months Unrealized Losses	27	273
12 months or Longer Fair Value	1,493	583
12 months or Longer Unrealized Losses	$ 347	$ 135