INVESTMENTS - Held-to-Maturity Debt Securities (Details) - USD ($) $ in Millions	Jun. 30, 2024		Mar. 31, 2024	Dec. 31, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 15,690			$ 17,824
Allowance for Credit Loss	5		$ 5	5	$ 5	$ 6	$ 7
Total fixed maturity securities, held-to- maturity, amortized cost	15,685	[1]		17,819
Gross Unrealized Gains	890			1,838
Gross Unrealized Losses	5			0
Fair   Value	16,570			19,657
Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	15,690			17,824
Allowance for Credit Loss	5			5
Total fixed maturity securities, held-to- maturity, amortized cost	15,685			17,819
Gross Unrealized Gains	890			1,838
Gross Unrealized Losses	5			0
Fair   Value	16,570			19,657
Japan government and agencies | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	15,040			17,085
Allowance for Credit Loss	2			2
Total fixed maturity securities, held-to- maturity, amortized cost	15,038			17,083
Gross Unrealized Gains	834			1,746
Gross Unrealized Losses	5			0
Fair   Value	15,867			18,829
Municipalities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	232			266
Fair   Value	256			307
Municipalities | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	232			266
Allowance for Credit Loss	0			0
Total fixed maturity securities, held-to- maturity, amortized cost	232			266
Gross Unrealized Gains	24			41
Gross Unrealized Losses	0			0
Fair   Value	256			307
Public utilities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	31			34
Fair   Value	32			38
Public utilities | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	31			34
Allowance for Credit Loss	0			0
Total fixed maturity securities, held-to- maturity, amortized cost	31			34
Gross Unrealized Gains	1			4
Gross Unrealized Losses	0			0
Fair   Value	32			38
Sovereign and supranational
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	368			418
Fair   Value	398			462
Sovereign and supranational | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	371			421
Allowance for Credit Loss	3			3
Total fixed maturity securities, held-to- maturity, amortized cost	368			418
Gross Unrealized Gains	30			44
Gross Unrealized Losses	0			0
Fair   Value	398			462
Other corporate
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	16			18
Fair   Value	17			21
Other corporate | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	16			18
Allowance for Credit Loss	0			0
Total fixed maturity securities, held-to- maturity, amortized cost	16			18
Gross Unrealized Gains	1			3
Gross Unrealized Losses	0			0
Fair   Value	$ 17			$ 21

[1] Net of allowance for credit losses