INVESTMENTS - Held-to-Maturity Debt Securities (Details) - USD ($) $ in Millions	Dec. 31, 2021		Dec. 31, 2020
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 22,008		$ 24,474
Allowance for Credit Losses	8		10
Net Carrying Amount	22,000	[1]	24,464
Gross Unrealized Gains	4,869		5,935
Gross Unrealized Losses	0		0
Fair Value	26,869		30,399
Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	22,008		24,474
Allowance for Credit Losses	8		10
Net Carrying Amount	22,000		24,464
Gross Unrealized Gains	4,869		5,935
Gross Unrealized Losses	0		0
Fair Value	26,869		30,399
Japan government and agencies | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	21,089		23,448
Allowance for Credit Losses	3		3
Net Carrying Amount	21,086		23,445
Gross Unrealized Gains	4,613		5,625
Gross Unrealized Losses	0		0
Fair Value	25,699		29,070
Municipalities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	335		377
Fair Value	436		499
Municipalities | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	335		377
Allowance for Credit Losses	0		0
Net Carrying Amount	335		377
Gross Unrealized Gains	101		122
Gross Unrealized Losses	0		0
Fair Value	436		499
Public utilities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	43		47
Fair Value	55		61
Public utilities | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	44		48
Allowance for Credit Losses	1		1
Net Carrying Amount	43		47
Gross Unrealized Gains	12		14
Gross Unrealized Losses	0		0
Fair Value	55		61
Sovereign and supranational
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	514		571
Fair Value	650		736
Sovereign and supranational | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	518		577
Allowance for Credit Losses	4		6
Net Carrying Amount	514		571
Gross Unrealized Gains	136		165
Gross Unrealized Losses	0		0
Fair Value	650		736
Other corporate
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	22		24
Fair Value	29		33
Other corporate | Yen-denominated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	22		24
Allowance for Credit Losses	0		0
Net Carrying Amount	22		24
Gross Unrealized Gains	7		9
Gross Unrealized Losses	0		0
Fair Value	$ 29		$ 33

[1] Net of allowance for credit losses