INVESTMENTS - Held-to-Maturity Debt Securities (Details) - USD ($) $ in Millions	Mar. 31, 2025		Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 16,893		$ 15,971
Allowance for Credit Loss	5		5	$ 5	$ 5
Total fixed maturity securities, held-to- maturity, amortized cost	16,888	[1]	15,966
Gross Unrealized Gains	402		815
Gross Unrealized Losses	155		9
Fair Value	17,135		16,772
Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	16,893		15,971
Allowance for Credit Loss	5		5
Total fixed maturity securities, held-to- maturity, amortized cost	16,888		15,966
Gross Unrealized Gains	402		815
Gross Unrealized Losses	155		9
Fair Value	17,135		16,772
Japan government and agencies | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	16,195		15,311
Allowance for Credit Loss	2		2
Total fixed maturity securities, held-to- maturity, amortized cost	16,193		15,309
Gross Unrealized Gains	368		759
Gross Unrealized Losses	155		9
Fair Value	16,406		16,059
Municipalities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	249		235
Fair Value	260		257
Municipalities | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	249		235
Allowance for Credit Loss	0		0
Total fixed maturity securities, held-to- maturity, amortized cost	249		235
Gross Unrealized Gains	11		22
Gross Unrealized Losses	0		0
Fair Value	260		257
Public utilities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	33		32
Fair Value	33		33
Public utilities | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	33		32
Allowance for Credit Loss	0		0
Total fixed maturity securities, held-to- maturity, amortized cost	33		32
Gross Unrealized Gains	0		1
Gross Unrealized Losses	0		0
Fair Value	33		33
Sovereign and supranational
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	396		374
Fair Value	418		405
Sovereign and supranational | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	399		377
Allowance for Credit Loss	3		3
Total fixed maturity securities, held-to- maturity, amortized cost	396		374
Gross Unrealized Gains	22		31
Gross Unrealized Losses	0		0
Fair Value	418		405
Other corporate
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	17		16
Fair Value	18		18
Other corporate | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	17		16
Allowance for Credit Loss	0		0
Total fixed maturity securities, held-to- maturity, amortized cost	17		16
Gross Unrealized Gains	1		2
Gross Unrealized Losses	0		0
Fair Value	$ 18		$ 18

[1] Net of allowance for credit losses