ALLOWANCE FOR CREDIT LOSSES - Allowance for Credit Losses Roll Forward (Details) - USD ($) $ in Millions		3 Months Ended			12 Months Ended
	Jan. 01, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	$ 12,783			$ 12,783	$ 24,956	$ 12,783	$ 12,315
Gross credit losses on loans					(6,720)	(9,263)	(9,341)
Gross recoveries on loans					1,825	1,652	1,573
Net credit losses on loans (NCLs)					(4,895)	(7,611)	(7,768)
Net reserve builds (releases)					(7,283)	7,635	364
Net specific reserve builds (releases) for loans					(715)	676	86
Total provision for credit losses on loans (PCLL)					(3,103)	15,922	8,218
Initial allowance for credit losses on newly purchased credit-deteriorated assets during the period					0	4	0
Other, net					(503)	100	18
ACLL at end of year					16,455	24,956	12,783
Allowance for credit losses on unfunded commitments
Allowance for credit losses on unfunded commitments (ACLUC) at beginning of period	1,456			1,456	2,655	1,456	1,367
Provision (release) for credit losses on unfunded lending commitments					(788)	1,446	92
Other, net					4	(53)	(3)
ACLUC at end of period					1,871	2,655	1,456
Total allowance for credit losses on loans, leases and unfunded lending commitments					18,326	27,611	14,239
Sales or transfers of various consumer loan portfolios to held-for-sale
Other liabilities, at fair value					74,920	59,983
Previously reported
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	12,783			12,783		12,783
ACLL at end of year							12,783
Variable post-charge-off third-party collection costs
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	(443)	$ (426)		(443)		(443)
Total provision for credit losses on loans (PCLL)		122	$ 339	(18)
ACLL at end of year	(443)	$ (122)	$ (426)				(443)
Reclassification adjustment
Allowance for credit losses on unfunded commitments
Allowance for credit losses on unfunded commitments (ACLUC) at beginning of period					(68)
ACLUC at end of period						(68)
Sales or transfers of various consumer loan portfolios to held-for-sale
Other liabilities, at fair value						68
Adjustment to opening balance for CECL adoption
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	4,201			4,201		4,201
Net reserve builds (releases)	4,900
ACLL at end of year	4,100						4,201
Allowance for credit losses on unfunded commitments
Allowance for credit losses on unfunded commitments (ACLUC) at beginning of period	(194)			(194)		(194)
ACLUC at end of period							(194)
Adjusted balance
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	16,541			16,541		16,541
ACLL at end of year							16,541
Consumer
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	9,897			9,897	19,554	9,897	9,504
Gross credit losses on loans					(6,198)	(8,191)	(8,854)
Gross recoveries on loans					1,698	1,566	1,478
Net credit losses on loans (NCLs)					(4,500)	(6,625)	(7,376)
Net reserve builds (releases)					(5,029)	4,745	268
Net specific reserve builds (releases) for loans					(437)	394	107
Initial allowance for credit losses on newly purchased credit-deteriorated assets during the period					0	4
Other, net					(472)	35	18
ACLL at end of year					13,616	19,554	9,897
Sales or transfers of various consumer loan portfolios to held-for-sale
Transfer of real estate loan portfolios					0	(4)	(42)
Sales or transfers of various consumer loan portfolios to HFS					(370)	(4)	(42)
Consumer | Australia Consumer Loan
Sales or transfers of various consumer loan portfolios to held-for-sale
Reclass consumer to held-for sale					(280)	0	0
Consumer | Philippines Consumer Loan
Sales or transfers of various consumer loan portfolios to held-for-sale
Reclass consumer to held-for sale					(90)	0	0
Consumer | Variable post-charge-off third-party collection costs
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	(443)			(443)		(443)
ACLL at end of year							(443)
Consumer | Adjustment to opening balance for CECL adoption
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	4,922			4,922		4,922
ACLL at end of year							4,922
Consumer | Adjusted balance
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	14,376			14,376		14,376
ACLL at end of year							14,376
Corporate
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	2,886			2,886	5,402	2,886	2,811
Gross credit losses on loans					(522)	(1,072)	(487)
Gross recoveries on loans					127	86	95
Net credit losses on loans (NCLs)					(395)	(986)	(392)
Net reserve builds (releases)					(2,254)	2,890	96
Net specific reserve builds (releases) for loans					(278)	282	(21)
Initial allowance for credit losses on newly purchased credit-deteriorated assets during the period					0	0
Other, net					(31)	65	0
ACLL at end of year					2,839	5,402	2,886
Sales or transfers of various consumer loan portfolios to held-for-sale
FX translation					$ (133)	104	60
Corporate | Variable post-charge-off third-party collection costs
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	0			0		0
ACLL at end of year							0
Corporate | Adjustment to opening balance for CECL adoption
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	(721)			(721)		(721)
ACLL at end of year							(721)
Corporate | Adjusted balance
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	$ 2,165			$ 2,165		$ 2,165
ACLL at end of year							$ 2,165