ALLOWANCE FOR CREDIT LOSSES - Allowance for Credit Losses Roll Forward by Segment (Details) - USD ($) $ in Millions		12 Months Ended
	Jan. 01, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Jan. 01, 2023	Sep. 30, 2020	Jun. 30, 2020
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	$ 16,541	$ 16,455	$ 24,956	$ 16,541
Gross credit losses on loans		(5,156)	(6,720)	(9,263)
Gross recoveries on loans		1,367	1,825	1,652
Replenishment of NCLs		3,789	4,895	7,611
Net reserve builds (releases) for loans		937	(7,283)	7,635
Net specific reserve builds (releases) for loans		19	(715)	676
Initial allowance for credit losses on newly purchased credit-deteriorated assets during the period		0	0	4
Other		(437)	(503)	100
ACLL at end of year		16,974	16,455	24,956
Allowance for credit losses on loans
Collectively evaluated		16,053	15,430
Individually evaluated		919	1,025
Total allowance for credit losses on loans		16,974	16,455	24,956
Loans, net of unearned income
Collectively evaluated		647,704	656,265
Individually evaluated		4,043	5,301
Loans held at fair value		5,360	6,082
Total		657,221	667,767
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)
ACLL at end of year	(443)
Allowance for credit losses on loans
Total allowance for credit losses on loans	(443)					$ (122)	$ (426)
Purchased credit deteriorated
Allowance for credit losses on loans
Purchased credit deteriorated		2	0
Loans, net of unearned income
Purchased credit deteriorated		114	119
Corporate
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	1,911	2,415	4,776	1,911
Gross credit losses on loans		(278)	(500)	(976)
Gross recoveries on loans		100	114	76
Replenishment of NCLs		178	386	900
Net reserve builds (releases) for loans		374	(2,075)	2,551
Net specific reserve builds (releases) for loans		65	(255)	249
Initial allowance for credit losses on newly purchased credit-deteriorated assets during the period		0	0	0
Other		1	(31)	65
ACLL at end of year		2,855	2,415	4,776
Allowance for credit losses on loans
Collectively evaluated		2,532	2,203
Individually evaluated		323	212
Total allowance for credit losses on loans		2,855	2,415	4,776
Loans, net of unearned income
Collectively evaluated		282,909	283,610
Individually evaluated		1,122	1,553
Loans held at fair value		5,123	6,070
Total		289,154	291,233
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
Allowance for credit losses on loans
Total allowance for credit losses on loans
Corporate | Purchased credit deteriorated
Allowance for credit losses on loans
Purchased credit deteriorated		0	0
Loans, net of unearned income
Purchased credit deteriorated		0	0
Consumer
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	14,630	14,040	20,180	14,630
Gross credit losses on loans		(4,878)	(6,220)	(8,287)
Gross recoveries on loans		1,267	1,711	1,576
Replenishment of NCLs		3,611	4,509	6,711
Net reserve builds (releases) for loans		563	(5,208)	5,084
Net specific reserve builds (releases) for loans		(46)	(460)	427
Initial allowance for credit losses on newly purchased credit-deteriorated assets during the period		0	0	4
Other		(438)	(472)	35
ACLL at end of year		14,119	14,040	20,180
Allowance for credit losses on loans
Collectively evaluated		13,521	13,227
Individually evaluated		596	813
Total allowance for credit losses on loans		14,119	14,040	20,180
Loans, net of unearned income
Collectively evaluated		364,795	372,655
Individually evaluated		2,921	3,748
Loans held at fair value		237	12
Total		368,067	376,534
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)
Allowance for credit losses on loans
Total allowance for credit losses on loans
Consumer | Purchased credit deteriorated
Allowance for credit losses on loans
Purchased credit deteriorated		2	0
Loans, net of unearned income
Purchased credit deteriorated		$ 114	119
Cumulative effect of adoption
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	4,201			4,201
Net reserve builds (releases) for loans	4,900
ACLL at end of year	4,100
Allowance for credit losses on loans
Total allowance for credit losses on loans	4,100				$ (350)
Cumulative effect of adoption | Corporate
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	(816)			(816)
Allowance for credit losses on loans
Total allowance for credit losses on loans
Cumulative effect of adoption | Consumer
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year	$ 5,017			5,017
Allowance for credit losses on loans
Total allowance for credit losses on loans
Adjusted balance
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of year			$ 24,956
ACLL at end of year				24,956
Allowance for credit losses on loans
Total allowance for credit losses on loans				$ 24,956