INVESTMENTS - Securities Lending Transactions Accounted for as Secured Borrowings (Detail) - USD ($) $ in Millions		Dec. 31, 2025	Dec. 31, 2024
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions		$ 3,989	$ 2,037
Gross amount of recognized liabilities for securities lending		3,989	2,037
Japan government and agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions		2,920	1,027
Public utilities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions		54	34
Banks/financial institutions
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions		150	193
Other corporate
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions		865	783
Maturity Overnight and Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions	[1]	1,069	1,010
Maturity Overnight and Continuous | Japan government and agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions	[1]	0	0
Maturity Overnight and Continuous | Public utilities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions	[1]	54	34
Maturity Overnight and Continuous | Banks/financial institutions
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions	[1]	150	193
Maturity Overnight and Continuous | Other corporate
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions	[1]	865	783
Maturity up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions		1,591	1,027
Maturity up to 30 Days | Japan government and agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions		1,591	1,027
Maturity up to 30 Days | Public utilities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions		0	0
Maturity up to 30 Days | Banks/financial institutions
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions		0	0
Maturity up to 30 Days | Other corporate
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions		0	$ 0
Maturity 30 to 90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions		1,329
Maturity 30 to 90 Days | Japan government and agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions		1,329
Maturity 30 to 90 Days | Public utilities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions		0
Maturity 30 to 90 Days | Banks/financial institutions
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions		0
Maturity 30 to 90 Days | Other corporate
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending transactions		$ 0

[1] The related loaned security, under the Company's U.S. securities lending program, can be returned to the Company at the transferee's discretion; therefore, they are classified as Overnight and Continuous.