INVESTMENTS - Fair Value and Gross Unrealized Losses for Securities That Have Been in Continuous Unrealized Loss Position (Detail) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Fixed maturity securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	$ 19,522	$ 7,914
Total Unrealized Losses	937	239
Less than 12 months Fair Value	13,526	2,948
Less than 12 months Unrealized Losses	477	42
12 months or Longer Fair Value	5,996	4,966
12 months or Longer Unrealized Losses	460	197
Yen-denominated | Fixed maturity securities | Japan government and agencies
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	7,780	2,868
Total Unrealized Losses	345	61
Less than 12 months Fair Value	4,264	445
Less than 12 months Unrealized Losses	123	3
12 months or Longer Fair Value	3,516	2,423
12 months or Longer Unrealized Losses	222	58
Yen-denominated | Fixed maturity securities | Municipalities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	216	187
Total Unrealized Losses	15	5
Less than 12 months Fair Value	96	53
Less than 12 months Unrealized Losses	4	0
12 months or Longer Fair Value	120	134
12 months or Longer Unrealized Losses	11	5
Yen-denominated | Fixed maturity securities | Mortgage- and asset-backed securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	79	33
Total Unrealized Losses	3	1
Less than 12 months Fair Value	49	0
Less than 12 months Unrealized Losses	0	0
12 months or Longer Fair Value	30	33
12 months or Longer Unrealized Losses	3	1
Yen-denominated | Fixed maturity securities | Public utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	598	26
Total Unrealized Losses	17	2
Less than 12 months Fair Value	546	0
Less than 12 months Unrealized Losses	14	0
12 months or Longer Fair Value	52	26
12 months or Longer Unrealized Losses	3	2
Yen-denominated | Fixed maturity securities | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1,453	541
Total Unrealized Losses	77	26
Less than 12 months Fair Value	1,209	274
Less than 12 months Unrealized Losses	47	4
12 months or Longer Fair Value	244	267
12 months or Longer Unrealized Losses	30	22
Yen-denominated | Fixed maturity securities | Banks/financial institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	3,594	2,074
Total Unrealized Losses	168	72
Less than 12 months Fair Value	2,576	1,011
Less than 12 months Unrealized Losses	86	16
12 months or Longer Fair Value	1,018	1,063
12 months or Longer Unrealized Losses	82	56
Dollar-denominated | Fixed maturity securities | Municipalities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	258	82
Total Unrealized Losses	16	2
Less than 12 months Fair Value	243	79
Less than 12 months Unrealized Losses	14	2
12 months or Longer Fair Value	15	3
12 months or Longer Unrealized Losses	2	0
Dollar-denominated | Fixed maturity securities | Mortgage- and asset-backed securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	549	278
Total Unrealized Losses	23	2
Less than 12 months Fair Value	533	278
Less than 12 months Unrealized Losses	23	2
12 months or Longer Fair Value	16	0
12 months or Longer Unrealized Losses	0	0
Dollar-denominated | Fixed maturity securities | Public utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	535	130
Total Unrealized Losses	29	5
Less than 12 months Fair Value	459	70
Less than 12 months Unrealized Losses	23	2
12 months or Longer Fair Value	76	60
12 months or Longer Unrealized Losses	6	3
Dollar-denominated | Fixed maturity securities | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	3,835	1,365
Total Unrealized Losses	207	53
Less than 12 months Fair Value	3,011	458
Less than 12 months Unrealized Losses	118	8
12 months or Longer Fair Value	824	907
12 months or Longer Unrealized Losses	89	45
Dollar-denominated | Fixed maturity securities | Sovereign and supranational
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	34	37
Total Unrealized Losses	8	6
Less than 12 months Fair Value	5	6
Less than 12 months Unrealized Losses	1	1
12 months or Longer Fair Value	29	31
12 months or Longer Unrealized Losses	7	5
Dollar-denominated | Fixed maturity securities | Banks/financial institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	590	292
Total Unrealized Losses	26	3
Less than 12 months Fair Value	535	274
Less than 12 months Unrealized Losses	21	3
12 months or Longer Fair Value	55	18
12 months or Longer Unrealized Losses	5	0
Dollar-denominated | Fixed maturity securities | U.S. government and agencies
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	1	1
Total Unrealized Losses	3	1
Less than 12 months Fair Value	0	0
Less than 12 months Unrealized Losses	3	1
12 months or Longer Fair Value	1	1
12 months or Longer Unrealized Losses	$ 0	$ 0