INVESTMENTS - Held-to-Maturity Debt Securities (Details) - USD ($) $ in Millions	Mar. 31, 2022		Dec. 31, 2021
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	$ 20,680		$ 22,008
Allowance for Credit Loss	8		8
Net Carrying Amount	20,672	[1]	22,000
Gross Unrealized Gains	3,913		4,869
Gross Unrealized Losses	0		0
Fair Value	24,585		26,869
Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	20,680		22,008
Allowance for Credit Loss	8		8
Net Carrying Amount	20,672		22,000
Gross Unrealized Gains	3,913		4,869
Gross Unrealized Losses	0		0
Fair Value	24,585		26,869
Japan government and agencies | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	19,817		21,089
Allowance for Credit Loss	3		3
Net Carrying Amount	19,814		21,086
Gross Unrealized Gains	3,712		4,613
Gross Unrealized Losses	0		0
Fair Value	23,526		25,699
Municipalities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	315		335
Fair Value	398		436
Municipalities | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	315		335
Allowance for Credit Loss	0		0
Net Carrying Amount	315		335
Gross Unrealized Gains	83		101
Gross Unrealized Losses	0		0
Fair Value	398		436
Public utilities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	40		43
Fair Value	50		55
Public utilities | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	41		44
Allowance for Credit Loss	1		1
Net Carrying Amount	40		43
Gross Unrealized Gains	10		12
Gross Unrealized Losses	0		0
Fair Value	50		55
Sovereign and supranational
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	483		514
Fair Value	584		650
Sovereign and supranational | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	487		518
Allowance for Credit Loss	4		4
Net Carrying Amount	483		514
Gross Unrealized Gains	101		136
Gross Unrealized Losses	0		0
Fair Value	584		650
Other corporate
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	20		22
Fair Value	27		29
Other corporate | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	20		22
Allowance for Credit Loss	0		0
Net Carrying Amount	20		22
Gross Unrealized Gains	7		7
Gross Unrealized Losses	0		0
Fair Value	$ 27		$ 29

[1] Net of allowance for credit losses