INVESTMENTS - Held-to-Maturity Debt Securities (Details) - USD ($) $ in Millions	Sep. 30, 2024		Jun. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 17,703			$ 17,824
Allowance for Credit Loss	5		$ 5	5	$ 5	$ 5	$ 7
Total fixed maturity securities, held-to- maturity, amortized cost	17,698	[1]		17,819
Gross Unrealized Gains	1,277			1,838
Gross Unrealized Losses	0			0
Fair Value	18,975			19,657
Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	17,703			17,824
Allowance for Credit Loss	5			5
Total fixed maturity securities, held-to- maturity, amortized cost	17,698			17,819
Gross Unrealized Gains	1,277			1,838
Gross Unrealized Losses	0			0
Fair Value	18,975			19,657
Japan government and agencies | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	16,970			17,085
Allowance for Credit Loss	2			2
Total fixed maturity securities, held-to- maturity, amortized cost	16,968			17,083
Gross Unrealized Gains	1,200			1,746
Gross Unrealized Losses	0			0
Fair Value	18,168			18,829
Municipalities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	262			266
Fair Value	293			307
Municipalities | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	262			266
Allowance for Credit Loss	0			0
Total fixed maturity securities, held-to- maturity, amortized cost	262			266
Gross Unrealized Gains	31			41
Gross Unrealized Losses	0			0
Fair Value	293			307
Public utilities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	35			34
Fair Value	37			38
Public utilities | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	35			34
Allowance for Credit Loss	0			0
Total fixed maturity securities, held-to- maturity, amortized cost	35			34
Gross Unrealized Gains	2			4
Gross Unrealized Losses	0			0
Fair Value	37			38
Sovereign and supranational
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	415			418
Fair Value	457			462
Sovereign and supranational | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	418			421
Allowance for Credit Loss	3			3
Total fixed maturity securities, held-to- maturity, amortized cost	415			418
Gross Unrealized Gains	42			44
Gross Unrealized Losses	0			0
Fair Value	457			462
Other corporate
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	18			18
Fair Value	20			21
Other corporate | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	18			18
Allowance for Credit Loss	0			0
Total fixed maturity securities, held-to- maturity, amortized cost	18			18
Gross Unrealized Gains	2			3
Gross Unrealized Losses	0			0
Fair Value	$ 20			$ 21

[1] Net of allowance for credit losses