INVESTMENTS - Available-for-sale Debt Securities (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 71,035	$ 85,369
Allowance for Credit Losses	0	0
Gross Unrealized Gains	6,162	13,566
Gross Unrealized Losses	3,554	239
Fair Value	73,643	98,696
Yen-denominated
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	40,253	51,160
Allowance for Credit Losses	0	0
Gross Unrealized Gains	3,129	6,994
Gross Unrealized Losses	1,957	167
Fair Value	41,425	57,987
Dollar-denominated
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	30,782	34,209
Allowance for Credit Losses	0	0
Gross Unrealized Gains	3,033	6,572
Gross Unrealized Losses	1,597	72
Fair Value	32,218	40,709
Japan government and agencies \| Yen-denominated
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	23,342	30,335
Allowance for Credit Losses	0	0
Gross Unrealized Gains	1,558	3,343
Gross Unrealized Losses	1,158	61
Fair Value	23,742	33,617
Municipalities
Debt Securities, Available-for-sale [Line Items]
Fair Value	2,276	3,036
Municipalities \| Yen-denominated
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	947	1,192
Allowance for Credit Losses	0	0
Gross Unrealized Gains	164	322
Gross Unrealized Losses	40	5
Fair Value	1,071	1,509
Municipalities \| Dollar-denominated
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,252	1,340
Allowance for Credit Losses	0	0
Gross Unrealized Gains	58	189
Gross Unrealized Losses	105	2
Fair Value	1,205	1,527
Mortgage- and asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Fair Value	2,009	1,246
Mortgage- and asset-backed securities \| Yen-denominated
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	231	300
Allowance for Credit Losses	0	0
Gross Unrealized Gains	9	19
Gross Unrealized Losses	8	1
Fair Value	232	318
Mortgage- and asset-backed securities \| Dollar-denominated
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,732	897
Allowance for Credit Losses	0	0
Gross Unrealized Gains	119	33
Gross Unrealized Losses	74	2
Fair Value	1,777	928
Public utilities
Debt Securities, Available-for-sale [Line Items]
Fair Value	7,350	10,051
Public utilities \| Yen-denominated
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,605	4,462
Allowance for Credit Losses	0	0
Gross Unrealized Gains	303	906
Gross Unrealized Losses	87	2
Fair Value	3,821	5,366
Public utilities \| Dollar-denominated
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,398	3,781
Allowance for Credit Losses	0	0
Gross Unrealized Gains	312	909
Gross Unrealized Losses	181	5
Fair Value	3,529	4,685
Sovereign and supranational
Debt Securities, Available-for-sale [Line Items]
Fair Value	862	1,115
Sovereign and supranational \| Yen-denominated
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	603	760
Allowance for Credit Losses	0	0
Gross Unrealized Gains	34	82
Gross Unrealized Losses	1	0
Fair Value	636	842
Sovereign and supranational \| Dollar-denominated
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	194	222
Allowance for Credit Losses	0	0
Gross Unrealized Gains	45	57
Gross Unrealized Losses	13	6
Fair Value	226	273
Banks/financial institutions
Debt Securities, Available-for-sale [Line Items]
Fair Value	9,031	11,591
Banks/financial institutions \| Yen-denominated
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,813	6,963
Allowance for Credit Losses	0	0
Gross Unrealized Gains	365	787
Gross Unrealized Losses	399	72
Fair Value	5,779	7,678
Banks/financial institutions \| Dollar-denominated
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,002	3,169
Allowance for Credit Losses	0	0
Gross Unrealized Gains	347	747
Gross Unrealized Losses	97	3
Fair Value	3,252	3,913
Other corporate
Debt Securities, Available-for-sale [Line Items]
Fair Value	28,205	37,837
Other corporate \| Yen-denominated
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,712	7,148
Allowance for Credit Losses	0	0
Gross Unrealized Gains	696	1,535
Gross Unrealized Losses	264	26
Fair Value	6,144	8,657
Other corporate \| Dollar-denominated
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	21,028	24,604
Allowance for Credit Losses	0	0
Gross Unrealized Gains	2,152	4,629
Gross Unrealized Losses	1,119	53
Fair Value	22,061	29,180
U.S. government and agencies \| Dollar-denominated
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	176	196
Allowance for Credit Losses	0	0
Gross Unrealized Gains	0	8
Gross Unrealized Losses	8	1
Fair Value	$ 168	$ 203

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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